Compiler: Add early error for output path being a directory.

- Introduce new `Path` type and an array of build paths on the build context.
- Resolve input and output paths/files early (before parsing).
- Error early if inputs are missing or outputs are directories.
- Plumb new file path generation into linker stage instead of its adhoc method.

TODO:
- Remove more adhoc file path generation in parser and linker stage.
- Make intermediate object file generation use new path system.
- Round out and robustify Path helper functions.

15 files changed, 674 insertions, 404 deletions

diff --git a/.gitignore b/.gitignore
index e8b3d3050..d03a86fd7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -269,6 +269,7 @@ bin/
 # - Linux/MacOS
 odin
 odin.dSYM
+*.bin
 
 # shared collection
 shared/
diff --git a/Makefile b/Makefile
index 82150c6a2..1a1c93180 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
-all: debug demo
+all: debug
 
 demo:
-	./odin run examples/demo/demo.odin
+	./odin run examples/demo
 
 report:
 	./odin report
diff --git a/build_odin.sh b/build_odin.sh
index aef3f2836..4810cafd2 100755
--- a/build_odin.sh
+++ b/build_odin.sh
@@ -102,7 +102,7 @@ build_odin() {
 }
 
 run_demo() {
-	./odin run examples/demo/demo.odin -file
+	./odin run examples/demo
 }
 
 case $OS in
@@ -147,4 +147,4 @@ if [[ $# -eq 1 ]]; then
 	exit 0
 else
 	panic "Too many arguments!"
-fi
+fi
\ No newline at end of file
diff --git a/src/build_settings.cpp b/src/build_settings.cpp
index 2f3eb03a5..0b582eac8 100644
--- a/src/build_settings.cpp
+++ b/src/build_settings.cpp
@@ -3,7 +3,6 @@
 #include <sys/sysctl.h>
 #endif
 
-
 // #if defined(GB_SYSTEM_WINDOWS)
 // #define DEFAULT_TO_THREADED_CHECKER
 // #endif
@@ -198,6 +197,22 @@ enum RelocMode : u8 {
 	RelocMode_DynamicNoPIC,
 };
 
+enum BuildPath : u8 {
+	BuildPath_Main_Package,     // Input  Path to the package directory (or file) we're building.
+	BuildPath_RC,               // Input  Path for .rc  file, can be set with `-resource:`.
+	BuildPath_RES,              // Output Path for .res file, generated from previous.
+	BuildPath_Win_SDK_Root,     // windows_sdk_root
+	BuildPath_Win_SDK_UM_Lib,   // windows_sdk_um_library_path
+	BuildPath_Win_SDK_UCRT_Lib, // windows_sdk_ucrt_library_path
+	BuildPath_VS_EXE,           // vs_exe_path
+	BuildPath_VS_LIB,           // vs_library_path
+
+	BuildPath_Output,           // Output Path for .exe, .dll, .so, etc. Can be overridden with `-out:`.
+	BuildPath_PDB,              // Output Path for .pdb file, can be overridden with `-pdb-name:`.
+
+	BuildPathCOUNT,
+};
+
 // This stores the information for the specify architecture of this build
 struct BuildContext {
 	// Constants
@@ -226,9 +241,13 @@ struct BuildContext {
 
 	bool show_help;
 
+	Array<Path> build_paths;   // Contains `Path` objects to output filename, pdb, resource and intermediate files.
+	                           // BuildPath enum contains the indices of paths we know *before* the work starts.
+
 	String out_filepath;
 	String resource_filepath;
 	String pdb_filepath;
+
 	bool   has_resource;
 	String link_flags;
 	String extra_linker_flags;
@@ -300,8 +319,6 @@ struct BuildContext {
 
 };
 
-
-
 gb_global BuildContext build_context = {0};
 
 bool global_warnings_as_errors(void) {
@@ -605,28 +622,6 @@ bool allow_check_foreign_filepath(void) {
 // is_abs_path
 // has_subdir
 
-enum TargetFileValidity : u8 {
-	TargetFileValidity_Invalid,
-
-	TargetFileValidity_Writable_File,
-	TargetFileValidity_No_Write_Permission,
-	TargetFileValidity_Directory,
-
-	TargetTargetFileValidity_COUNT,
-};
-
-TargetFileValidity set_output_filename(void) {
-	// Assembles the output filename from build_context information.
-	// Returns `true`  if it doesn't exist or is a file.
-	// Returns `false` if a directory or write-protected file.
-
-
-
-
-	return TargetFileValidity_Writable_File;
-}
-
-
 String const WIN32_SEPARATOR_STRING = {cast(u8 *)"\\", 1};
 String const NIX_SEPARATOR_STRING   = {cast(u8 *)"/",  1};
 
@@ -973,7 +968,6 @@ char *token_pos_to_string(TokenPos const &pos) {
 	return s;
 }
 
-
 void init_build_context(TargetMetrics *cross_target) {
 	BuildContext *bc = &build_context;
 
@@ -1152,8 +1146,178 @@ void init_build_context(TargetMetrics *cross_target) {
 
 	bc->optimization_level = gb_clamp(bc->optimization_level, 0, 3);
 
-
-
 	#undef LINK_FLAG_X64
 	#undef LINK_FLAG_386
 }
+
+#if defined(GB_SYSTEM_WINDOWS)
+// NOTE(IC): In order to find Visual C++ paths without relying on environment variables.
+// NOTE(Jeroen): No longer needed in `main.cpp -> linker_stage`. We now resolve those paths in `init_build_paths`.
+#include "microsoft_craziness.h"
+#endif
+
+// NOTE(Jeroen): Set/create the output and other paths and report an error as appropriate.
+// We've previously called `parse_build_flags`, so `out_filepath` should be set.
+bool init_build_paths(String init_filename) {
+	gbAllocator   ha = heap_allocator();
+	BuildContext *bc = &build_context;
+
+	// NOTE(Jeroen): We're pre-allocating BuildPathCOUNT slots so that certain paths are always at the same enumerated index.
+	array_init(&bc->build_paths, permanent_allocator(), BuildPathCOUNT);
+
+	// [BuildPathMainPackage] Turn given init path into a `Path`, which includes normalizing it into a full path.
+	bc->build_paths[BuildPath_Main_Package] = path_from_string(ha, init_filename);
+
+	bool produces_output_file = false;
+	if (bc->command_kind == Command_doc && bc->cmd_doc_flags & CmdDocFlag_DocFormat) {
+		produces_output_file = true;
+	} else if (bc->command_kind & Command__does_build) {
+		produces_output_file = true;
+	}
+
+	if (!produces_output_file) {
+		// Command doesn't produce output files. We're done.
+		return true;
+	}
+
+	#if defined(GB_SYSTEM_WINDOWS)
+		if (bc->resource_filepath.len > 0) {
+			bc->build_paths[BuildPath_RC]      = path_from_string(ha, bc->resource_filepath);
+			bc->build_paths[BuildPath_RES]     = path_from_string(ha, bc->resource_filepath);
+			bc->build_paths[BuildPath_RC].ext  = copy_string(ha, STR_LIT("rc"));
+			bc->build_paths[BuildPath_RES].ext = copy_string(ha, STR_LIT("res"));
+		}
+
+		if (bc->pdb_filepath.len > 0) {
+			bc->build_paths[BuildPath_PDB]          = path_from_string(ha, bc->pdb_filepath);
+		}
+
+		if ((bc->command_kind & Command__does_build) && (!bc->ignore_microsoft_magic)) {
+			// NOTE(ic): It would be nice to extend this so that we could specify the Visual Studio version that we want instead of defaulting to the latest.
+			Find_Result_Utf8 find_result = find_visual_studio_and_windows_sdk_utf8();
+
+			if (find_result.windows_sdk_version == 0) {
+				gb_printf_err("Windows SDK not found.\n");
+				return false;
+			}
+
+			GB_ASSERT(find_result.windows_sdk_um_library_path.len > 0);
+			GB_ASSERT(find_result.windows_sdk_ucrt_library_path.len > 0);
+
+			if (find_result.windows_sdk_root.len > 0) {
+				bc->build_paths[BuildPath_Win_SDK_Root]     = path_from_string(ha, find_result.windows_sdk_root);
+			}
+
+			if (find_result.windows_sdk_um_library_path.len > 0) {
+				bc->build_paths[BuildPath_Win_SDK_UM_Lib]   = path_from_string(ha, find_result.windows_sdk_um_library_path);
+			}
+
+			if (find_result.windows_sdk_ucrt_library_path.len > 0) {
+				bc->build_paths[BuildPath_Win_SDK_UCRT_Lib] = path_from_string(ha, find_result.windows_sdk_ucrt_library_path);
+			}
+
+			if (find_result.vs_exe_path.len > 0) {
+				bc->build_paths[BuildPath_VS_EXE]           = path_from_string(ha, find_result.vs_exe_path);
+			}
+
+			if (find_result.vs_library_path.len > 0) {
+				bc->build_paths[BuildPath_VS_LIB]           = path_from_string(ha, find_result.vs_library_path);
+			}
+
+			gb_free(ha, find_result.windows_sdk_root.text);
+			gb_free(ha, find_result.windows_sdk_um_library_path.text);
+			gb_free(ha, find_result.windows_sdk_ucrt_library_path.text);
+			gb_free(ha, find_result.vs_exe_path.text);
+			gb_free(ha, find_result.vs_library_path.text);
+
+		}
+	#endif
+
+	// All the build targets and OSes.
+	String output_extension;
+
+	if (bc->command_kind == Command_doc && bc->cmd_doc_flags & CmdDocFlag_DocFormat) {
+		output_extension = STR_LIT("odin-doc");
+	} else if (is_arch_wasm()) {
+		output_extension = STR_LIT("wasm");
+	} else if (build_context.build_mode == BuildMode_Executable) {
+		// By default use a .bin executable extension.
+		output_extension = STR_LIT("bin");
+
+		if (build_context.metrics.os == TargetOs_windows) {
+			output_extension = STR_LIT("exe");
+		} else if (build_context.cross_compiling && selected_target_metrics->metrics == &target_essence_amd64) {
+			output_extension = make_string(nullptr, 0);
+		}
+	} else if (build_context.build_mode == BuildMode_DynamicLibrary) {
+		// By default use a .so shared library extension.
+		output_extension = STR_LIT("so");
+
+		if (build_context.metrics.os == TargetOs_windows) {
+			output_extension = STR_LIT("dll");
+		} else if (build_context.metrics.os == TargetOs_darwin) {
+			output_extension = STR_LIT("dylib");
+		}
+	} else if (build_context.build_mode == BuildMode_Object) {
+		// By default use a .o object extension.
+		output_extension = STR_LIT("o");
+
+		if (build_context.metrics.os == TargetOs_windows) {
+			output_extension = STR_LIT("obj");
+		}
+	} else if (build_context.build_mode == BuildMode_Assembly) {
+		// By default use a .S asm extension.
+		output_extension = STR_LIT("S");
+	} else if (build_context.build_mode == BuildMode_LLVM_IR) {
+		output_extension = STR_LIT("ll");
+	} else {
+		GB_PANIC("Unhandled build mode/target combination.\n");
+	}
+
+	if (bc->out_filepath.len > 0) {
+		bc->build_paths[BuildPath_Output] = path_from_string(ha, bc->out_filepath);
+	} else {
+		String output_name = remove_directory_from_path(init_filename);
+		output_name        = remove_extension_from_path(output_name);
+		output_name        = copy_string(ha, string_trim_whitespace(output_name));
+
+		/*
+		NOTE(Jeroen): This fallback substitution can't be made at this stage.
+		if (gen->output_name.len == 0) {
+			gen->output_name = c->info.init_scope->pkg->name;
+		}
+		*/
+		Path output_path = path_from_string(ha, output_name);
+
+		#ifndef GB_SYSTEM_WINDOWS
+			char cwd[4096];
+			getcwd(&cwd[0], 4096);
+
+			const u8 * cwd_str = (const u8 *)&cwd[0];
+			output_path.basename = copy_string(ha, make_string(cwd_str, strlen(cwd)));
+		#endif
+
+		// Replace extension.
+		if (output_path.ext.len > 0) {
+			gb_free(ha, output_path.ext.text);
+		}
+		output_path.ext  = copy_string(ha, output_extension);
+
+		bc->build_paths[BuildPath_Output] = output_path;
+	}
+
+	// Do we have an extension? We might not if the output filename was supplied.
+	if (bc->build_paths[BuildPath_Output].ext.len == 0) {
+		bc->build_paths[BuildPath_Output].ext = copy_string(ha, output_extension);
+	}
+
+	// Check if output path is a directory.
+	if (path_is_directory(bc->build_paths[BuildPath_Output])) {
+		String output_file = path_to_string(ha, bc->build_paths[BuildPath_Output]);
+		defer (gb_free(ha, output_file.text));
+		gb_printf_err("Output path %.*s is a directory.\n", LIT(output_file));
+		return false;
+	}
+
+	return true;
+}
\ No newline at end of file
diff --git a/src/common.cpp b/src/common.cpp
index aaacda04b..94248fb62 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -675,262 +675,7 @@ wchar_t **command_line_to_wargv(wchar_t *cmd_line, int *_argc) {
 
 #endif
 
-
-#if defined(GB_SYSTEM_WINDOWS)
-	bool path_is_directory(String path) {
-		gbAllocator a = heap_allocator();
-		String16 wstr = string_to_string16(a, path);
-		defer (gb_free(a, wstr.text));
-
-		i32 attribs = GetFileAttributesW(wstr.text);
-		if (attribs < 0) return false;
-
-		return (attribs & FILE_ATTRIBUTE_DIRECTORY) != 0;
-	}
-
-#else
-	bool path_is_directory(String path) {
-		gbAllocator a = heap_allocator();
-		char *copy = cast(char *)copy_string(a, path).text;
-		defer (gb_free(a, copy));
-
-		struct stat s;
-		if (stat(copy, &s) == 0) {
-			return (s.st_mode & S_IFDIR) != 0;
-		}
-		return false;
-	}
-#endif
-
-
-String path_to_full_path(gbAllocator a, String path) {
-	gbAllocator ha = heap_allocator();
-	char *path_c = gb_alloc_str_len(ha, cast(char *)path.text, path.len);
-	defer (gb_free(ha, path_c));
-
-	char *fullpath = gb_path_get_full_name(a, path_c);
-	String res = string_trim_whitespace(make_string_c(fullpath));
-#if defined(GB_SYSTEM_WINDOWS)
-	for (isize i = 0; i < res.len; i++) {
-		if (res.text[i] == '\\') {
-			res.text[i] = '/';
-		}
-	}
-#endif
-	return res;
-}
-
-
-
-struct FileInfo {
-	String name;
-	String fullpath;
-	i64    size;
-	bool   is_dir;
-};
-
-enum ReadDirectoryError {
-	ReadDirectory_None,
-
-	ReadDirectory_InvalidPath,
-	ReadDirectory_NotExists,
-	ReadDirectory_Permission,
-	ReadDirectory_NotDir,
-	ReadDirectory_Empty,
-	ReadDirectory_Unknown,
-
-	ReadDirectory_COUNT,
-};
-
-i64 get_file_size(String path) {
-	char *c_str = alloc_cstring(heap_allocator(), path);
-	defer (gb_free(heap_allocator(), c_str));
-
-	gbFile f = {};
-	gbFileError err = gb_file_open(&f, c_str);
-	defer (gb_file_close(&f));
-	if (err != gbFileError_None) {
-		return -1;
-	}
-	return gb_file_size(&f);
-}
-
-
-#if defined(GB_SYSTEM_WINDOWS)
-ReadDirectoryError read_directory(String path, Array<FileInfo> *fi) {
-	GB_ASSERT(fi != nullptr);
-
-	gbAllocator a = heap_allocator();
-
-	while (path.len > 0) {
-		Rune end = path[path.len-1];
-		if (end == '/') {
-			path.len -= 1;
-		} else if (end == '\\') {
-			path.len -= 1;
-		} else {
-			break;
-		}
-	}
-
-	if (path.len == 0) {
-		return ReadDirectory_InvalidPath;
-	}
-	{
-		char *c_str = alloc_cstring(a, path);
-		defer (gb_free(a, c_str));
-
-		gbFile f = {};
-		gbFileError file_err = gb_file_open(&f, c_str);
-		defer (gb_file_close(&f));
-
-		switch (file_err) {
-		case gbFileError_Invalid:    return ReadDirectory_InvalidPath;
-		case gbFileError_NotExists:  return ReadDirectory_NotExists;
-		// case gbFileError_Permission: return ReadDirectory_Permission;
-		}
-	}
-
-	if (!path_is_directory(path)) {
-		return ReadDirectory_NotDir;
-	}
-
-
-	char *new_path = gb_alloc_array(a, char, path.len+3);
-	defer (gb_free(a, new_path));
-
-	gb_memmove(new_path, path.text, path.len);
-	gb_memmove(new_path+path.len, "/*", 2);
-	new_path[path.len+2] = 0;
-
-	String np = make_string(cast(u8 *)new_path, path.len+2);
-	String16 wstr = string_to_string16(a, np);
-	defer (gb_free(a, wstr.text));
-
-	WIN32_FIND_DATAW file_data = {};
-	HANDLE find_file = FindFirstFileW(wstr.text, &file_data);
-	if (find_file == INVALID_HANDLE_VALUE) {
-		return ReadDirectory_Unknown;
-	}
-	defer (FindClose(find_file));
-
-	array_init(fi, a, 0, 100);
-
-	do {
-		wchar_t *filename_w = file_data.cFileName;
-		i64 size = cast(i64)file_data.nFileSizeLow;
-		size |= (cast(i64)file_data.nFileSizeHigh) << 32;
-		String name = string16_to_string(a, make_string16_c(filename_w));
-		if (name == "." || name == "..") {
-			gb_free(a, name.text);
-			continue;
-		}
-
-		String filepath = {};
-		filepath.len = path.len+1+name.len;
-		filepath.text = gb_alloc_array(a, u8, filepath.len+1);
-		defer (gb_free(a, filepath.text));
-		gb_memmove(filepath.text, path.text, path.len);
-		gb_memmove(filepath.text+path.len, "/", 1);
-		gb_memmove(filepath.text+path.len+1, name.text, name.len);
-
-		FileInfo info = {};
-		info.name = name;
-		info.fullpath = path_to_full_path(a, filepath);
-		info.size = size;
-		info.is_dir = (file_data.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0;
-		array_add(fi, info);
-	} while (FindNextFileW(find_file, &file_data));
-
-	if (fi->count == 0) {
-		return ReadDirectory_Empty;
-	}
-
-	return ReadDirectory_None;
-}
-#elif defined(GB_SYSTEM_LINUX) || defined(GB_SYSTEM_OSX) || defined(GB_SYSTEM_FREEBSD) || defined(GB_SYSTEM_OPENBSD)
-
-#include <dirent.h>
-
-ReadDirectoryError read_directory(String path, Array<FileInfo> *fi) {
-	GB_ASSERT(fi != nullptr);
-
-	gbAllocator a = heap_allocator();
-
-	char *c_path = alloc_cstring(a, path);
-	defer (gb_free(a, c_path));
-
-	DIR *dir = opendir(c_path);
-	if (!dir) {
-		switch (errno) {
-		case ENOENT:
-			return ReadDirectory_NotExists;
-		case EACCES:
-			return ReadDirectory_Permission;
-		case ENOTDIR:
-			return ReadDirectory_NotDir;
-		default:
-			// ENOMEM: out of memory
-			// EMFILE: per-process limit on open fds reached
-			// ENFILE: system-wide limit on total open files reached
-			return ReadDirectory_Unknown;
-		}
-		GB_PANIC("unreachable");
-	}
-
-	array_init(fi, a, 0, 100);
-
-	for (;;) {
-		struct dirent *entry = readdir(dir);
-		if (entry == nullptr) {
-			break;
-		}
-
-		String name = make_string_c(entry->d_name);
-		if (name == "." || name == "..") {
-			continue;
-		}
-
-		String filepath = {};
-		filepath.len = path.len+1+name.len;
-		filepath.text = gb_alloc_array(a, u8, filepath.len+1);
-		defer (gb_free(a, filepath.text));
-		gb_memmove(filepath.text, path.text, path.len);
-		gb_memmove(filepath.text+path.len, "/", 1);
-		gb_memmove(filepath.text+path.len+1, name.text, name.len);
-		filepath.text[filepath.len] = 0;
-
-
-		struct stat dir_stat = {};
-
-		if (stat((char *)filepath.text, &dir_stat)) {
-			continue;
-		}
-
-		if (S_ISDIR(dir_stat.st_mode)) {
-			continue;
-		}
-
-		i64 size = dir_stat.st_size;
-
-		FileInfo info = {};
-		info.name = name;
-		info.fullpath = path_to_full_path(a, filepath);
-		info.size = size;
-		array_add(fi, info);
-	}
-
-	if (fi->count == 0) {
-		return ReadDirectory_Empty;
-	}
-
-	return ReadDirectory_None;
-}
-#else
-#error Implement read_directory
-#endif
-
-
+#include "path.cpp"
 
 struct LoadedFile {
 	void *handle;
diff --git a/src/gb/gb.h b/src/gb/gb.h
index b72a893f7..3b2d6434c 100644
--- a/src/gb/gb.h
+++ b/src/gb/gb.h
@@ -6273,20 +6273,44 @@ char *gb_path_get_full_name(gbAllocator a, char const *path) {
 #else
 	char *p, *result, *fullpath = NULL;
 	isize len;
-	p = realpath(path, NULL);
-	fullpath = p;
-	if (p == NULL) {
-		// NOTE(bill): File does not exist
-		fullpath = cast(char *)path;
-	}
+	fullpath = realpath(path, NULL);
+
+	if (fullpath == NULL) {
+		// NOTE(Jeroen): Path doesn't exist.
+		if (gb_strlen(path) > 0 && path[0] == '/') {
+			// But it is an absolute path, so return as-is.
+
+			fullpath = (char *)path;
+			len      = gb_strlen(fullpath) + 1;
+			result   = gb_alloc_array(a, char, len + 1);
+
+			gb_memmove(result, fullpath, len);
+			result[len] = 0;
+
+		} else {
+			// Appears to be a relative path, so construct an absolute one relative to <cwd>.
+			char cwd[4096];
+			getcwd(&cwd[0], 4096);
+
+			isize path_len = gb_strlen(path);
+			isize cwd_len  = gb_strlen(cwd);
+			len            = cwd_len + 1 + path_len + 1;
+			result         = gb_alloc_array(a, char, len);
 
-	len = gb_strlen(fullpath);
+			gb_memmove(result, (void *)cwd, cwd_len);
+			result[cwd_len] = '/';
 
-	result = gb_alloc_array(a, char, len + 1);
-	gb_memmove(result, fullpath, len);
-	result[len] = 0;
-	free(p);
+			gb_memmove(result + cwd_len + 1, (void *)path, gb_strlen(path));
+			result[len] = 0;
 
+		}
+	} else {
+		len      = gb_strlen(fullpath) + 1;
+		result   = gb_alloc_array(a, char, len + 1);
+		gb_memmove(result, fullpath, len);
+		result[len] = 0;
+		free(fullpath);
+	}
 	return result;
 #endif
 }
diff --git a/src/llvm_backend.cpp b/src/llvm_backend.cpp
index f5cb84785..7781997f7 100644
--- a/src/llvm_backend.cpp
+++ b/src/llvm_backend.cpp
@@ -967,7 +967,12 @@ lbProcedure *lb_create_main_procedure(lbModule *m, lbProcedure *startup_runtime)
 }
 
 String lb_filepath_ll_for_module(lbModule *m) {
-	String path = m->gen->output_base;
+	String path = concatenate3_strings(permanent_allocator(),
+		build_context.build_paths[BuildPath_Output].basename,
+		STR_LIT("/"),
+		build_context.build_paths[BuildPath_Output].name
+	);
+
 	if (m->pkg) {
 		path = concatenate3_strings(permanent_allocator(), path, STR_LIT("-"), m->pkg->name);
 	} else if (USE_SEPARATE_MODULES) {
@@ -978,7 +983,12 @@ String lb_filepath_ll_for_module(lbModule *m) {
 	return path;
 }
 String lb_filepath_obj_for_module(lbModule *m) {
-	String path = m->gen->output_base;
+	String path = concatenate3_strings(permanent_allocator(),
+		build_context.build_paths[BuildPath_Output].basename,
+		STR_LIT("/"),
+		build_context.build_paths[BuildPath_Output].name
+	);
+
 	if (m->pkg) {
 		path = concatenate3_strings(permanent_allocator(), path, STR_LIT("-"), m->pkg->name);
 	}
diff --git a/src/llvm_backend_general.cpp b/src/llvm_backend_general.cpp
index 330059622..1a431a4ac 100644
--- a/src/llvm_backend_general.cpp
+++ b/src/llvm_backend_general.cpp
@@ -87,7 +87,6 @@ bool lb_init_generator(lbGenerator *gen, Checker *c) {
 		return false;
 	}
 
-
 	String init_fullpath = c->parser->init_fullpath;
 
 	if (build_context.out_filepath.len == 0) {
diff --git a/src/main.cpp b/src/main.cpp
index fc8792ceb..7b0364149 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -46,7 +46,6 @@ gb_global Timings global_timings = {0};
 #include "checker.cpp"
 #include "docs.cpp"
 
-
 #include "llvm_backend.cpp"
 
 #if defined(GB_SYSTEM_OSX)
@@ -57,16 +56,8 @@ gb_global Timings global_timings = {0};
 #endif
 
 #include "query_data.cpp"
-
-
-#if defined(GB_SYSTEM_WINDOWS)
-// NOTE(IC): In order to find Visual C++ paths without relying on environment variables.
-#include "microsoft_craziness.h"
-#endif
-
 #include "bug_report.cpp"
 
-
 // NOTE(bill): 'name' is used in debugging and profiling modes
 i32 system_exec_command_line_app(char const *name, char const *fmt, ...) {
 	isize const cmd_cap = 64<<20; // 64 MiB should be more than enough
@@ -130,34 +121,35 @@ i32 system_exec_command_line_app(char const *name, char const *fmt, ...) {
 }
 
 
-
-
 i32 linker_stage(lbGenerator *gen) {
 	i32 result = 0;
 	Timings *timings = &global_timings;
 
-	String output_base = gen->output_base;
+	String output_filename = path_to_string(heap_allocator(), build_context.build_paths[BuildPath_Output]);
+	debugf("Linking %.*s\n", LIT(output_filename));
+
+	// TOOD(Jeroen): Make a `build_paths[BuildPath_Object] to avoid `%.*s.o`.
 
 	if (is_arch_wasm()) {
 		timings_start_section(timings, str_lit("wasm-ld"));
 
 	#if defined(GB_SYSTEM_WINDOWS)
 		result = system_exec_command_line_app("wasm-ld",
-			"\"%.*s\\bin\\wasm-ld\" \"%.*s.wasm.o\" -o \"%.*s.wasm\" %.*s %.*s",
+			"\"%.*s\\bin\\wasm-ld\" \"%.*s.o\" -o \"%.*s\" %.*s %.*s",
 			LIT(build_context.ODIN_ROOT),
-			LIT(output_base), LIT(output_base), LIT(build_context.link_flags), LIT(build_context.extra_linker_flags));
+			LIT(output_filename), LIT(output_filename), LIT(build_context.link_flags), LIT(build_context.extra_linker_flags));
 	#else
 		result = system_exec_command_line_app("wasm-ld",
-			"wasm-ld \"%.*s.wasm.o\" -o \"%.*s.wasm\" %.*s %.*s",
-			LIT(output_base), LIT(output_base), LIT(build_context.link_flags), LIT(build_context.extra_linker_flags));
+			"wasm-ld \"%.*s.o\" -o \"%.*s\" %.*s %.*s",
+			LIT(output_filename), LIT(output_filename), LIT(build_context.link_flags), LIT(build_context.extra_linker_flags));
 	#endif
 		return result;
 	}
 
 	if (build_context.cross_compiling && selected_target_metrics->metrics == &target_essence_amd64) {
-#ifdef GB_SYSTEM_UNIX
+#if defined(GB_SYSTEM_UNIX) 
 		result = system_exec_command_line_app("linker", "x86_64-essence-gcc \"%.*s.o\" -o \"%.*s\" %.*s %.*s",
-			LIT(output_base), LIT(output_base), LIT(build_context.link_flags), LIT(build_context.extra_linker_flags));
+			LIT(output_filename), LIT(output_filename), LIT(build_context.link_flags), LIT(build_context.extra_linker_flags));
 #else
 		gb_printf_err("Linking for cross compilation for this platform is not yet supported (%.*s %.*s)\n",
 			LIT(target_os_names[build_context.metrics.os]),
@@ -181,28 +173,11 @@ i32 linker_stage(lbGenerator *gen) {
 		gbString lib_str = gb_string_make(heap_allocator(), "");
 		defer (gb_string_free(lib_str));
 
-		char const *output_ext = "exe";
 		gbString link_settings = gb_string_make_reserve(heap_allocator(), 256);
 		defer (gb_string_free(link_settings));
 
-
-		// NOTE(ic): It would be nice to extend this so that we could specify the Visual Studio version that we want instead of defaulting to the latest.
-		Find_Result_Utf8 find_result = find_visual_studio_and_windows_sdk_utf8();
-
-		if (find_result.windows_sdk_version == 0) {
-			gb_printf_err("Windows SDK not found.\n");
-			exit(1);
-		}
-
-		if (build_context.ignore_microsoft_magic) {
-			find_result = {};
-		}
-
 		// Add library search paths.
-		if (find_result.vs_library_path.len > 0) {
-			GB_ASSERT(find_result.windows_sdk_um_library_path.len > 0);
-			GB_ASSERT(find_result.windows_sdk_ucrt_library_path.len > 0);
-
+		if (build_context.build_paths[BuildPath_VS_LIB].basename.len > 0) {
 			String path = {};
 			auto add_path = [&](String path) {
 				if (path[path.len-1] == '\\') {
@@ -210,9 +185,9 @@ i32 linker_stage(lbGenerator *gen) {
 				}
 				link_settings = gb_string_append_fmt(link_settings, " /LIBPATH:\"%.*s\"", LIT(path));
 			};
-			add_path(find_result.windows_sdk_um_library_path);
-			add_path(find_result.windows_sdk_ucrt_library_path);
-			add_path(find_result.vs_library_path);
+			add_path(build_context.build_paths[BuildPath_Win_SDK_UM_Lib].basename);
+			add_path(build_context.build_paths[BuildPath_Win_SDK_UCRT_Lib].basename);
+			add_path(build_context.build_paths[BuildPath_VS_LIB].basename);
 		}
 
 
@@ -252,14 +227,14 @@ i32 linker_stage(lbGenerator *gen) {
 
 
 		if (build_context.build_mode == BuildMode_DynamicLibrary) {
-			output_ext = "dll";
 			link_settings = gb_string_append_fmt(link_settings, " /DLL");
 		} else {
 			link_settings = gb_string_append_fmt(link_settings, " /ENTRY:mainCRTStartup");
 		}
 
 		if (build_context.pdb_filepath != "") {
-			link_settings = gb_string_append_fmt(link_settings, " /PDB:%.*s", LIT(build_context.pdb_filepath));
+			String pdb_path = path_to_string(heap_allocator(), build_context.build_paths[BuildPath_PDB]);
+			link_settings = gb_string_append_fmt(link_settings, " /PDB:%.*s", LIT(pdb_path));
 		}
 
 		if (build_context.no_crt) {
@@ -300,13 +275,21 @@ i32 linker_stage(lbGenerator *gen) {
 			object_files = gb_string_append_fmt(object_files, "\"%.*s\" ", LIT(object_path));
 		}
 
+		String vs_exe_path = path_to_string(heap_allocator(), build_context.build_paths[BuildPath_VS_EXE]);
+		defer (gb_free(heap_allocator(), vs_exe_path.text));
+
 		char const *subsystem_str = build_context.use_subsystem_windows ? "WINDOWS" : "CONSOLE";
 		if (!build_context.use_lld) { // msvc
 			if (build_context.has_resource) {
+				String rc_path  = path_to_string(heap_allocator(), build_context.build_paths[BuildPath_RC]);
+				String res_path = path_to_string(heap_allocator(), build_context.build_paths[BuildPath_RES]);
+				defer (gb_free(heap_allocator(), rc_path.text));
+				defer (gb_free(heap_allocator(), res_path.text));
+
 				result = system_exec_command_line_app("msvc-link",
-					"\"rc.exe\" /nologo /fo \"%.*s.res\" \"%.*s.rc\"",
-					LIT(output_base),
-					LIT(build_context.resource_filepath)
+					"\"rc.exe\" /nologo /fo \"%.*s\" \"%.*s\"",
+					LIT(res_path),
+					LIT(rc_path)
 				);
 
 				if (result) {
@@ -314,13 +297,13 @@ i32 linker_stage(lbGenerator *gen) {
 				}
 
 				result = system_exec_command_line_app("msvc-link",
-					"\"%.*slink.exe\" %s \"%.*s.res\" -OUT:\"%.*s.%s\" %s "
+					"\"%.*slink.exe\" %s \"%.*s\" -OUT:\"%.*s\" %s "
 					"/nologo /incremental:no /opt:ref /subsystem:%s "
 					" %.*s "
 					" %.*s "
 					" %s "
 					"",
-					LIT(find_result.vs_exe_path), object_files, LIT(output_base), LIT(output_base), output_ext,
+					LIT(vs_exe_path), object_files, LIT(res_path), LIT(output_filename),
 					link_settings,
 					subsystem_str,
 					LIT(build_context.link_flags),
@@ -329,13 +312,13 @@ i32 linker_stage(lbGenerator *gen) {
 				  );
 			} else {
 				result = system_exec_command_line_app("msvc-link",
-					"\"%.*slink.exe\" %s -OUT:\"%.*s.%s\" %s "
+					"\"%.*slink.exe\" %s -OUT:\"%.*s\" %s "
 					"/nologo /incremental:no /opt:ref /subsystem:%s "
 					" %.*s "
 					" %.*s "
 					" %s "
 					"",
-					LIT(find_result.vs_exe_path), object_files, LIT(output_base), output_ext,
+					LIT(vs_exe_path), object_files, LIT(output_filename),
 					link_settings,
 					subsystem_str,
 					LIT(build_context.link_flags),
@@ -350,13 +333,13 @@ i32 linker_stage(lbGenerator *gen) {
 
 		} else { // lld
 			result = system_exec_command_line_app("msvc-lld-link",
-				"\"%.*s\\bin\\lld-link\" %s -OUT:\"%.*s.%s\" %s "
+				"\"%.*s\\bin\\lld-link\" %s -OUT:\"%.*s\" %s "
 				"/nologo /incremental:no /opt:ref /subsystem:%s "
 				" %.*s "
 				" %.*s "
 				" %s "
 				"",
-				LIT(build_context.ODIN_ROOT), object_files, LIT(output_base),output_ext,
+				LIT(build_context.ODIN_ROOT), object_files, LIT(output_filename),
 				link_settings,
 				subsystem_str,
 				LIT(build_context.link_flags),
@@ -415,7 +398,7 @@ i32 linker_stage(lbGenerator *gen) {
 				} else if (string_ends_with(lib, str_lit(".so"))) {
 					// dynamic lib, relative path to executable
 					// NOTE(vassvik): it is the user's responsibility to make sure the shared library files are visible
-					//                at runtimeto the executable
+					//                at runtime to the executable
 					lib_str = gb_string_append_fmt(lib_str, " -l:\"%s/%.*s\" ", cwd, LIT(lib));
 				} else {
 					// dynamic or static system lib, just link regularly searching system library paths
@@ -431,9 +414,6 @@ i32 linker_stage(lbGenerator *gen) {
 			object_files = gb_string_append_fmt(object_files, "\"%.*s\" ", LIT(object_path));
 		}
 
-		// Unlike the Win32 linker code, the output_ext includes the dot, because
-		// typically executable files on *NIX systems don't have extensions.
-		String output_ext = {};
 		gbString link_settings = gb_string_make_reserve(heap_allocator(), 32);
 
 		if (build_context.no_crt) {
@@ -461,26 +441,12 @@ i32 linker_stage(lbGenerator *gen) {
 			// correctly this way since all the other dependencies provided implicitly
 			// by the compiler frontend are still needed and most of the command
 			// line arguments prepared previously are incompatible with ld.
-			//
-			// Shared libraries are .dylib on MacOS and .so on Linux.
-			if (build_context.metrics.os == TargetOs_darwin) {
-				output_ext = STR_LIT(".dylib");
-			} else {
-				output_ext = STR_LIT(".so");
-			}
 			link_settings = gb_string_appendc(link_settings, "-Wl,-init,'_odin_entry_point' ");
 			link_settings = gb_string_appendc(link_settings, "-Wl,-fini,'_odin_exit_point' ");
 		} else if (build_context.metrics.os != TargetOs_openbsd) {
 			// OpenBSD defaults to PIE executable. do not pass -no-pie for it.
 			link_settings = gb_string_appendc(link_settings, "-no-pie ");
 		}
-		if (build_context.out_filepath.len > 0) {
-			//NOTE(thebirk): We have a custom -out arguments, so we should use the extension from that
-			isize pos = string_extension_position(build_context.out_filepath);
-			if (pos > 0) {
-				output_ext = substring(build_context.out_filepath, pos, build_context.out_filepath.len);
-			}
-		}
 
 		gbString platform_lib_str = gb_string_make(heap_allocator(), "");
 		defer (gb_string_free(platform_lib_str));
@@ -507,7 +473,7 @@ i32 linker_stage(lbGenerator *gen) {
 		defer (gb_string_free(link_command_line));
 
 		link_command_line = gb_string_appendc(link_command_line, object_files);
-		link_command_line = gb_string_append_fmt(link_command_line, " -o \"%.*s%.*s\" ", LIT(output_base), LIT(output_ext));
+		link_command_line = gb_string_append_fmt(link_command_line, " -o \"%.*s\" ", LIT(output_filename));
 		link_command_line = gb_string_append_fmt(link_command_line, " %s ", platform_lib_str);
 		link_command_line = gb_string_append_fmt(link_command_line, " %s ", lib_str);
 		link_command_line = gb_string_append_fmt(link_command_line, " %.*s ", LIT(build_context.link_flags));
@@ -524,9 +490,7 @@ i32 linker_stage(lbGenerator *gen) {
 		if (build_context.ODIN_DEBUG) {
 			// NOTE: macOS links DWARF symbols dynamically. Dsymutil will map the stubs in the exe
 			// to the symbols in the object file
-			result = system_exec_command_line_app("dsymutil",
-				"dsymutil %.*s%.*s", LIT(output_base), LIT(output_ext)
-			);
+			result = system_exec_command_line_app("dsymutil", "dsymutil %.*s", LIT(output_filename));
 
 			if (result) {
 				return result;
@@ -1526,6 +1490,10 @@ bool parse_build_flags(Array<String> args) {
 									gb_printf_err("Invalid -resource path %.*s, missing .rc\n", LIT(path));
 									bad_flags = true;
 									break;
+								} else if (!gb_file_exists((const char *)path.text)) {
+									gb_printf_err("Invalid -resource path %.*s, file does not exist.\n", LIT(path));
+									bad_flags = true;
+									break;
 								}
 								build_context.resource_filepath = substring(path, 0, string_extension_position(path));
 								build_context.has_resource = true;
@@ -1540,6 +1508,11 @@ bool parse_build_flags(Array<String> args) {
 							String path = value.value_string;
 							path = string_trim_whitespace(path);
 							if (is_build_flag_path_valid(path)) {
+								if (path_is_directory(path)) {
+									gb_printf_err("Invalid -pdb-name path. %.*s, is a directory.\n", LIT(path));
+									bad_flags = true;
+									break;									
+								}
 								// #if defined(GB_SYSTEM_WINDOWS)
 								// 	String ext = path_extension(path);
 								// 	if (ext != ".pdb") {
@@ -2666,6 +2639,8 @@ int main(int arg_count, char const **arg_ptr) {
 		return 1;
 	}
 
+	init_filename = copy_string(permanent_allocator(), init_filename);
+
 	if (init_filename == "-help" ||
 	    init_filename == "--help") {
 		build_context.show_help = true;
@@ -2688,6 +2663,12 @@ int main(int arg_count, char const **arg_ptr) {
 				gb_printf_err("Did you mean `%.*s %.*s %.*s -file`?\n", LIT(args[0]), LIT(command), LIT(init_filename));
 				gb_printf_err("The `-file` flag tells it to treat a file as a self-contained package.\n");
 				return 1;
+			} else {
+				String const ext = str_lit(".odin");
+				if (!string_ends_with(init_filename, ext)) {
+					gb_printf_err("Expected either a directory or a .odin file, got '%.*s'\n", LIT(init_filename));
+					return 1;
+				}
 			}
 		}
 	}
@@ -2709,13 +2690,24 @@ int main(int arg_count, char const **arg_ptr) {
 			get_fullpath_relative(heap_allocator(), odin_root_dir(), str_lit("shared")));
 	}
 
-
 	init_build_context(selected_target_metrics ? selected_target_metrics->metrics : nullptr);
 	// if (build_context.word_size == 4 && build_context.metrics.os != TargetOs_js) {
 	// 	print_usage_line(0, "%.*s 32-bit is not yet supported for this platform", LIT(args[0]));
 	// 	return 1;
 	// }
 
+	// Set and check build paths...
+	if (!init_build_paths(init_filename)) {
+		return 1;
+	}
+
+	if (build_context.show_debug_messages) {
+		for_array(i, build_context.build_paths) {
+			String build_path = path_to_string(heap_allocator(), build_context.build_paths[i]);
+			debugf("build_paths[%ld]: %.*s\n", i, LIT(build_path));
+		}		
+	}
+
 	init_global_thread_pool();
 	defer (thread_pool_destroy(&global_thread_pool));
 
@@ -2732,6 +2724,8 @@ int main(int arg_count, char const **arg_ptr) {
 	}
 	defer (destroy_parser(parser));
 
+	// TODO(jeroen): Remove the `init_filename` param.
+	// Let's put that on `build_context.build_paths[0]` instead.
 	if (parse_packages(parser, init_filename) != ParseFile_None) {
 		return 1;
 	}
@@ -2810,16 +2804,14 @@ int main(int arg_count, char const **arg_ptr) {
 	}
 
 	if (run_output) {
+		String exe_name = path_to_string(heap_allocator(), build_context.build_paths[BuildPath_Output]);
+		defer (gb_free(heap_allocator(), exe_name.text));
+
 	#if defined(GB_SYSTEM_WINDOWS)
-		return system_exec_command_line_app("odin run", "%.*s.exe %.*s", LIT(gen->output_base), LIT(run_args_string));
+		return system_exec_command_line_app("odin run", "%.*s %.*s", LIT(exe_name), LIT(run_args_string));
 	#else
-		//NOTE(thebirk): This whole thing is a little leaky
-		String output_ext = {};
-		String complete_path = concatenate_strings(permanent_allocator(), gen->output_base, output_ext);
-		complete_path = path_to_full_path(permanent_allocator(), complete_path);
-		return system_exec_command_line_app("odin run", "\"%.*s\" %.*s", LIT(complete_path), LIT(run_args_string));
+		return system_exec_command_line_app("odin run", "\"%.*s\" %.*s", LIT(exe_name), LIT(run_args_string));
 	#endif
 	}
-
 	return 0;
 }
diff --git a/src/parser.cpp b/src/parser.cpp
index 767119aa8..df7f908a6 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -5751,7 +5751,7 @@ ParseFileError parse_packages(Parser *p, String init_filename) {
 			}
 		}
 	}
-	
+
 
 	{ // Add these packages serially and then process them parallel
 		mutex_lock(&p->wait_mutex);
diff --git a/src/path.cpp b/src/path.cpp
new file mode 100644
index 000000000..8d8e532b8
--- /dev/null
+++ b/src/path.cpp
@@ -0,0 +1,333 @@
+/*

+	Path handling utilities.

+*/

+

+#if defined(GB_SYSTEM_WINDOWS)

+	bool path_is_directory(String path) {

+		gbAllocator a = heap_allocator();

+		String16 wstr = string_to_string16(a, path);

+		defer (gb_free(a, wstr.text));

+

+		i32 attribs = GetFileAttributesW(wstr.text);

+		if (attribs < 0) return false;

+

+		return (attribs & FILE_ATTRIBUTE_DIRECTORY) != 0;

+	}

+

+#else

+	bool path_is_directory(String path) {

+		gbAllocator a = heap_allocator();

+		char *copy = cast(char *)copy_string(a, path).text;

+		defer (gb_free(a, copy));

+

+		struct stat s;

+		if (stat(copy, &s) == 0) {

+			return (s.st_mode & S_IFDIR) != 0;

+		}

+		return false;

+	}

+#endif

+

+

+String path_to_full_path(gbAllocator a, String path) {

+	gbAllocator ha = heap_allocator();

+	char *path_c = gb_alloc_str_len(ha, cast(char *)path.text, path.len);

+	defer (gb_free(ha, path_c));

+

+	char *fullpath = gb_path_get_full_name(a, path_c);

+	String res = string_trim_whitespace(make_string_c(fullpath));

+#if defined(GB_SYSTEM_WINDOWS)

+	for (isize i = 0; i < res.len; i++) {

+		if (res.text[i] == '\\') {

+			res.text[i] = '/';

+		}

+	}

+#endif

+	return copy_string(a, res);

+}

+

+struct Path {

+	String basename;

+	String name;

+	String ext;

+};

+

+// NOTE(Jeroen): Naively turns a Path into a string.

+String path_to_string(gbAllocator a, Path path) {

+	if (path.basename.len + path.name.len + path.ext.len == 0) {

+		return make_string(nullptr, 0);

+	}

+

+	isize len = path.basename.len + 1 + path.name.len + 1;

+	if (path.ext.len > 0) {

+		 len += path.ext.len + 1;

+	}

+

+	u8 *str = gb_alloc_array(a, u8, len);

+

+	isize i = 0;

+	gb_memmove(str+i, path.basename.text, path.basename.len); i += path.basename.len;

+	gb_memmove(str+i, "/", 1);                                i += 1;

+	gb_memmove(str+i, path.name.text,     path.name.len);     i += path.name.len;

+	if (path.ext.len > 0) {

+		gb_memmove(str+i, ".", 1);                            i += 1;

+		gb_memmove(str+i, path.ext.text,  path.ext.len);      i += path.ext.len;

+	}

+	str[i] = 0;

+

+	String res = make_string(str, i);

+	res        = string_trim_whitespace(res);

+	return res;

+}

+

+// NOTE(Jeroen): Naively turns a Path into a string, then normalizes it using `path_to_full_path`.

+String path_to_full_path(gbAllocator a, Path path) {

+	String temp = path_to_string(heap_allocator(), path);

+	defer (gb_free(heap_allocator(), temp.text));

+

+	return path_to_full_path(a, temp);

+}

+

+// NOTE(Jeroen): Takes a path like "odin" or "W:\Odin", turns it into a full path,

+// and then breaks it into its components to make a Path.

+Path path_from_string(gbAllocator a, String const &path) {

+	Path res = {};

+

+	if (path.len == 0) return res;

+

+	String fullpath = path_to_full_path(a, path);

+	defer (gb_free(heap_allocator(), fullpath.text));

+

+	res.basename     = directory_from_path(fullpath);

+	res.basename     = copy_string(a, res.basename);

+

+	if (string_ends_with(fullpath, '/')) {

+		// It's a directory. We don't need to tinker with the name and extension.

+		return res;

+	}

+

+	isize name_start = (res.basename.len > 0) ? res.basename.len + 1 : res.basename.len;

+	res.name         = substring(fullpath, name_start, fullpath.len);

+	res.name         = remove_extension_from_path(res.name);

+	res.name         = copy_string(a, res.name);

+

+	res.ext          = path_extension(fullpath, false); // false says not to include the dot.

+	res.ext          = copy_string(a, res.ext);

+	return res;

+}

+

+bool path_is_directory(Path path) {

+	String path_string = path_to_full_path(heap_allocator(), path);

+	defer (gb_free(heap_allocator(), path_string.text));

+

+	return path_is_directory(path_string);

+}

+

+struct FileInfo {

+	String name;

+	String fullpath;

+	i64    size;

+	bool   is_dir;

+};

+

+enum ReadDirectoryError {

+	ReadDirectory_None,

+

+	ReadDirectory_InvalidPath,

+	ReadDirectory_NotExists,

+	ReadDirectory_Permission,

+	ReadDirectory_NotDir,

+	ReadDirectory_Empty,

+	ReadDirectory_Unknown,

+

+	ReadDirectory_COUNT,

+};

+

+i64 get_file_size(String path) {

+	char *c_str = alloc_cstring(heap_allocator(), path);

+	defer (gb_free(heap_allocator(), c_str));

+

+	gbFile f = {};

+	gbFileError err = gb_file_open(&f, c_str);

+	defer (gb_file_close(&f));

+	if (err != gbFileError_None) {

+		return -1;

+	}

+	return gb_file_size(&f);

+}

+

+

+#if defined(GB_SYSTEM_WINDOWS)

+ReadDirectoryError read_directory(String path, Array<FileInfo> *fi) {

+	GB_ASSERT(fi != nullptr);

+

+	gbAllocator a = heap_allocator();

+

+	while (path.len > 0) {

+		Rune end = path[path.len-1];

+		if (end == '/') {

+			path.len -= 1;

+		} else if (end == '\\') {

+			path.len -= 1;

+		} else {

+			break;

+		}

+	}

+

+	if (path.len == 0) {

+		return ReadDirectory_InvalidPath;

+	}

+	{

+		char *c_str = alloc_cstring(a, path);

+		defer (gb_free(a, c_str));

+

+		gbFile f = {};

+		gbFileError file_err = gb_file_open(&f, c_str);

+		defer (gb_file_close(&f));

+

+		switch (file_err) {

+		case gbFileError_Invalid:    return ReadDirectory_InvalidPath;

+		case gbFileError_NotExists:  return ReadDirectory_NotExists;

+		// case gbFileError_Permission: return ReadDirectory_Permission;

+		}

+	}

+

+	if (!path_is_directory(path)) {

+		return ReadDirectory_NotDir;

+	}

+

+

+	char *new_path = gb_alloc_array(a, char, path.len+3);

+	defer (gb_free(a, new_path));

+

+	gb_memmove(new_path, path.text, path.len);

+	gb_memmove(new_path+path.len, "/*", 2);

+	new_path[path.len+2] = 0;

+

+	String np = make_string(cast(u8 *)new_path, path.len+2);

+	String16 wstr = string_to_string16(a, np);

+	defer (gb_free(a, wstr.text));

+

+	WIN32_FIND_DATAW file_data = {};

+	HANDLE find_file = FindFirstFileW(wstr.text, &file_data);

+	if (find_file == INVALID_HANDLE_VALUE) {

+		return ReadDirectory_Unknown;

+	}

+	defer (FindClose(find_file));

+

+	array_init(fi, a, 0, 100);

+

+	do {

+		wchar_t *filename_w = file_data.cFileName;

+		i64 size = cast(i64)file_data.nFileSizeLow;

+		size |= (cast(i64)file_data.nFileSizeHigh) << 32;

+		String name = string16_to_string(a, make_string16_c(filename_w));

+		if (name == "." || name == "..") {

+			gb_free(a, name.text);

+			continue;

+		}

+

+		String filepath = {};

+		filepath.len = path.len+1+name.len;

+		filepath.text = gb_alloc_array(a, u8, filepath.len+1);

+		defer (gb_free(a, filepath.text));

+		gb_memmove(filepath.text, path.text, path.len);

+		gb_memmove(filepath.text+path.len, "/", 1);

+		gb_memmove(filepath.text+path.len+1, name.text, name.len);

+

+		FileInfo info = {};

+		info.name = name;

+		info.fullpath = path_to_full_path(a, filepath);

+		info.size = size;

+		info.is_dir = (file_data.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0;

+		array_add(fi, info);

+	} while (FindNextFileW(find_file, &file_data));

+

+	if (fi->count == 0) {

+		return ReadDirectory_Empty;

+	}

+

+	return ReadDirectory_None;

+}

+#elif defined(GB_SYSTEM_LINUX) || defined(GB_SYSTEM_OSX) || defined(GB_SYSTEM_FREEBSD) || defined(GB_SYSTEM_OPENBSD)

+

+#include <dirent.h>

+

+ReadDirectoryError read_directory(String path, Array<FileInfo> *fi) {

+	GB_ASSERT(fi != nullptr);

+

+	gbAllocator a = heap_allocator();

+

+	char *c_path = alloc_cstring(a, path);

+	defer (gb_free(a, c_path));

+

+	DIR *dir = opendir(c_path);

+	if (!dir) {

+		switch (errno) {

+		case ENOENT:

+			return ReadDirectory_NotExists;

+		case EACCES:

+			return ReadDirectory_Permission;

+		case ENOTDIR:

+			return ReadDirectory_NotDir;

+		default:

+			// ENOMEM: out of memory

+			// EMFILE: per-process limit on open fds reached

+			// ENFILE: system-wide limit on total open files reached

+			return ReadDirectory_Unknown;

+		}

+		GB_PANIC("unreachable");

+	}

+

+	array_init(fi, a, 0, 100);

+

+	for (;;) {

+		struct dirent *entry = readdir(dir);

+		if (entry == nullptr) {

+			break;

+		}

+

+		String name = make_string_c(entry->d_name);

+		if (name == "." || name == "..") {

+			continue;

+		}

+

+		String filepath = {};

+		filepath.len = path.len+1+name.len;

+		filepath.text = gb_alloc_array(a, u8, filepath.len+1);

+		defer (gb_free(a, filepath.text));

+		gb_memmove(filepath.text, path.text, path.len);

+		gb_memmove(filepath.text+path.len, "/", 1);

+		gb_memmove(filepath.text+path.len+1, name.text, name.len);

+		filepath.text[filepath.len] = 0;

+

+

+		struct stat dir_stat = {};

+

+		if (stat((char *)filepath.text, &dir_stat)) {

+			continue;

+		}

+

+		if (S_ISDIR(dir_stat.st_mode)) {

+			continue;

+		}

+

+		i64 size = dir_stat.st_size;

+

+		FileInfo info = {};

+		info.name = name;

+		info.fullpath = path_to_full_path(a, filepath);

+		info.size = size;

+		array_add(fi, info);

+	}

+

+	if (fi->count == 0) {

+		return ReadDirectory_Empty;

+	}

+

+	return ReadDirectory_None;

+}

+#else

+#error Implement read_directory

+#endif

+

diff --git a/src/string.cpp b/src/string.cpp
index d3dbc6904..3515df48e 100644
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -245,15 +245,14 @@ gb_inline isize string_extension_position(String const &str) {
 	return dot_pos;
 }
 
-String path_extension(String const &str) {
+String path_extension(String const &str, bool include_dot = true) {
 	isize pos = string_extension_position(str);
 	if (pos < 0) {
 		return make_string(nullptr, 0);
 	}
-	return substring(str, pos, str.len);
+	return substring(str, include_dot ? pos : pos + 1, str.len);
 }
 
-
 String string_trim_whitespace(String str) {
 	while (str.len > 0 && rune_is_whitespace(str[str.len-1])) {
 		str.len--;
@@ -328,7 +327,10 @@ String directory_from_path(String const &s) {
 			break;
 		}
 	}
-	return substring(s, 0, i);
+	if (i >= 0) {
+		return substring(s, 0, i);	
+	}
+	return substring(s, 0, 0);
 }
 
 String concatenate_strings(gbAllocator a, String const &x, String const &y) {
diff --git a/tests/core/build.bat b/tests/core/build.bat
index 2f9ba672e..1973c22aa 100644
--- a/tests/core/build.bat
+++ b/tests/core/build.bat
@@ -5,61 +5,61 @@ python3 download_assets.py
 echo ---

 echo Running core:image tests

 echo ---

-%PATH_TO_ODIN% run image    %COMMON%

+%PATH_TO_ODIN% run image    %COMMON% -out:test_image

 

 echo ---

 echo Running core:compress tests

 echo ---

-%PATH_TO_ODIN% run compress %COMMON%

+%PATH_TO_ODIN% run compress %COMMON% -out:test_compress

 

 echo ---

 echo Running core:strings tests

 echo ---

-%PATH_TO_ODIN% run strings %COMMON%

+%PATH_TO_ODIN% run strings %COMMON% -out:test_strings

 

 echo ---

 echo Running core:hash tests

 echo ---

-%PATH_TO_ODIN% run hash %COMMON% -o:size

+%PATH_TO_ODIN% run hash %COMMON% -o:size -out:test_hash

 

 echo ---

 echo Running core:odin tests

 echo ---

-%PATH_TO_ODIN% run odin %COMMON% -o:size

+%PATH_TO_ODIN% run odin %COMMON% -o:size -out:test_odin

 

 echo ---

 echo Running core:crypto hash tests

 echo ---

-%PATH_TO_ODIN% run crypto %COMMON%

+%PATH_TO_ODIN% run crypto %COMMON% -out:test_crypto

 

 echo ---

 echo Running core:encoding tests

 echo ---

-%PATH_TO_ODIN% run encoding/hxa %COMMON%

-%PATH_TO_ODIN% run encoding/json %COMMON%

-%PATH_TO_ODIN% run encoding/varint %COMMON%

+%PATH_TO_ODIN% run encoding/hxa    %COMMON% -out:test_hxa

+%PATH_TO_ODIN% run encoding/json   %COMMON% -out:test_json

+%PATH_TO_ODIN% run encoding/varint %COMMON% -out:test_varint

 

 echo ---

 echo Running core:math/noise tests

 echo ---

-%PATH_TO_ODIN% run math/noise %COMMON%

+%PATH_TO_ODIN% run math/noise      %COMMON% -out:test_noise

 

 echo ---

 echo Running core:math tests

 echo ---

-%PATH_TO_ODIN% run math %COMMON%

+%PATH_TO_ODIN% run math %COMMON% -out:test_math

 

 echo ---

 echo Running core:math/linalg/glsl tests

 echo ---

-%PATH_TO_ODIN% run math/linalg/glsl %COMMON%

+%PATH_TO_ODIN% run math/linalg/glsl %COMMON% -out:test_glsl

 

 echo ---

 echo Running core:path/filepath tests

 echo ---

-%PATH_TO_ODIN% run path/filepath %COMMON%

+%PATH_TO_ODIN% run path/filepath %COMMON% -out:test_filepath

 

 echo ---

 echo Running core:reflect tests

 echo ---

-%PATH_TO_ODIN% run reflect %COMMON%

+%PATH_TO_ODIN% run reflect %COMMON% -out:test_reflect

diff --git a/tests/core/math/big/build.bat b/tests/core/math/big/build.bat
index 16bdbc8ca..ad199d775 100644
--- a/tests/core/math/big/build.bat
+++ b/tests/core/math/big/build.bat
@@ -4,7 +4,7 @@ set PATH_TO_ODIN==..\..\..\..\odin
 set TEST_ARGS=-fast-tests

 set TEST_ARGS=-no-random

 set TEST_ARGS=

-set OUT_NAME=math_big_test_library

+set OUT_NAME=math_big_test_library.dll

 set COMMON=-build-mode:shared -show-timings -no-bounds-check -define:MATH_BIG_EXE=false -vet -strict-style

 echo ---

 echo Running core:math/big tests

diff --git a/tests/issues/run.sh b/tests/issues/run.sh
index 117a9a5f1..91ec99e05 100755
--- a/tests/issues/run.sh
+++ b/tests/issues/run.sh
@@ -8,10 +8,10 @@ COMMON="-collection:tests=tests -out:tests/issues/build/test_issue"
 set -x
 
 ./odin build tests/issues/test_issue_829.odin $COMMON -file
-tests/issues/build/test_issue
+tests/issues/build/test_issue.bin
 
 ./odin build tests/issues/test_issue_1592.odin $COMMON -file
-tests/issues/build/test_issue
+tests/issues/build/test_issue.bin
 
 set +x