MSVC compatibility

.gitignore

@@ -60,3 +60,8 @@ dkms.conf
 /resources/y.tab.c
 /resources/y.tab.h
 /bin/
+
+#visual studio files
+.vs/
+.vscode/
+out/

CMakeLists.txt

@@ -53,18 +53,21 @@ llvm_map_components_to_libnames(llvm_libs ${LLVM_LINK_COMPONENTS})
 
 file(COPY ${CMAKE_SOURCE_DIR}/resources/lib DESTINATION ${CMAKE_BINARY_DIR})
 
-find_library(LLD_COFF NAMES lldCOFF.a liblldCOFF.a PATHS ${LLVM_LIBRARY_DIRS})
-find_library(LLD_COMMON NAMES lldCommon.a liblldCommon.a PATHS ${LLVM_LIBRARY_DIRS})
-find_library(LLD_CORE NAMES lldCore.a liblldCore.a PATHS ${LLVM_LIBRARY_DIRS})
-find_library(LLD_WASM NAMES lldWasm.a liblldWasm.a PATHS ${LLVM_LIBRARY_DIRS})
-find_library(LLD_MINGW NAMES lldMinGW.a liblldMinGW.a PATHS ${LLVM_LIBRARY_DIRS})
-find_library(LLD_ELF NAMES lldELF.a liblldELF.a PATHS ${LLVM_LIBRARY_DIRS})
-find_library(LLD_DRIVER NAMES lldDriver.a liblldDriver.a PATHS ${LLVM_LIBRARY_DIRS})
-find_library(LLD_READER_WRITER NAMES lldReaderWriter.a liblldReaderWriter.a PATHS ${LLVM_LIBRARY_DIRS})
-find_library(LLD_MACHO NAMES lldMachO.a liblldMachO.a PATHS ${LLVM_LIBRARY_DIRS})
-find_library(LLD_YAML NAMES lldYAML.a liblldYAML.a PATHS ${LLVM_LIBRARY_DIRS})
+# These don't seem to be reliable on windows.
+if(UNIX)
+    message(STATUS "using find_library")
+    find_library(LLD_COFF NAMES lldCOFF.a liblldCOFF.a PATHS ${LLVM_LIBRARY_DIRS})
+    find_library(LLD_COMMON NAMES lldCommon.a liblldCommon.a PATHS ${LLVM_LIBRARY_DIRS})
+    find_library(LLD_CORE NAMES lldCore.a liblldCore.a PATHS ${LLVM_LIBRARY_DIRS})
+    find_library(LLD_WASM NAMES lldWasm.a liblldWasm.a PATHS ${LLVM_LIBRARY_DIRS})
+    find_library(LLD_MINGW NAMES lldMinGW.a liblldMinGW.a PATHS ${LLVM_LIBRARY_DIRS})
+    find_library(LLD_ELF NAMES lldELF.a liblldELF.a PATHS ${LLVM_LIBRARY_DIRS})
+    find_library(LLD_DRIVER NAMES lldDriver.a liblldDriver.a PATHS ${LLVM_LIBRARY_DIRS})
+    find_library(LLD_READER_WRITER NAMES lldReaderWriter.a liblldReaderWriter.a PATHS ${LLVM_LIBRARY_DIRS})
+    find_library(LLD_MACHO NAMES lldMachO.a liblldMachO.a PATHS ${LLVM_LIBRARY_DIRS})
+    find_library(LLD_YAML NAMES lldYAML.a liblldYAML.a PATHS ${LLVM_LIBRARY_DIRS})
 
-set(lld_libs
+    set(lld_libs
         ${LLD_COFF}
         ${LLD_COMMON}
         ${LLD_WASM}
@@ -76,6 +79,8 @@ set(lld_libs
         ${LLD_YAML}
         ${LLD_CORE}
         )
+    message(STATUS "linking to llvm libs ${llvm_libs} ${lld_libs}")
+endif()
 add_library(c3c_wrappers STATIC wrapper/src/wrapper.cpp)
 
 add_executable(c3c
@@ -107,6 +112,7 @@ add_executable(c3c
         src/compiler/module.c
         src/compiler/llvm_codegen.c
         src/utils/stringutils.c
+        src/utils/find_msvc.c
         src/compiler/dwarf.h
         src/compiler/copying.c
         src/compiler/llvm_codegen_stmt.c
@@ -145,9 +151,11 @@ add_executable(c3c
         src/compiler/llvm_codegen_c_abi_riscv.c
         src/compiler/llvm_codegen_c_abi_wasm.c)
 
-target_compile_options(c3c PRIVATE -Wall -Werror -Wno-unknown-pragmas -Wno-unused-result
-        -Wno-unused-function -Wno-unused-variable -Wno-unused-parameter)
-
+if(NOT CMAKE_C_COMPILER_ID STREQUAL "MSVC")
+    message(STATUS "using gcc/clang warning switches")
+    target_compile_options(c3c PRIVATE -Wall -Werror -Wno-unknown-pragmas -Wno-unused-result
+            -Wno-unused-function -Wno-unused-variable -Wno-unused-parameter)
+endif()
 
 target_include_directories(c3c PRIVATE
         "${CMAKE_SOURCE_DIR}/src/")
@@ -158,9 +166,18 @@ target_include_directories(c3c_wrappers PRIVATE
 
 message(STATUS "Found LLD ${lld_libs}")
 
-target_link_libraries(c3c_wrappers ${llvm_libs} ${lld_libs})
-#target_link_libraries(c3c m ${llvm_libs} c3c_wrappers lldCommon lldCore lldCOFF lldWASM lldMinGW lldELF lldDriver lldReaderWriter lldMachO lldYAML)
-target_link_libraries(c3c m ${llvm_libs} c3c_wrappers ${lld_libs})
+if(UNIX)
+    message(STATUS "adding unix link params")
+    target_link_libraries(c3c_wrappers ${llvm_libs} ${lld_libs})
+    target_link_libraries(c3c m ${llvm_libs} c3c_wrappers ${lld_libs})
+else()
+    # todo: maybe get this from llvm-config somehow? it should be in LLVM_DIR\..\..\..\bin I think.
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -LIBPATH:C:\\llvm\\llvm\\build\\Release\\lib") # needed for lldCommon.lib
+    #set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -LIBPATH:${LLVM_LIBPATH}") # This doesn't seem to work for some reason
+    message(STATUS "${LLVM_LIBPATH}")
+    target_link_libraries(c3c debug ${llvm_libs} c3c_wrappers lldCommon lldCore lldCOFF lldWASM lldMinGW lldELF lldDriver lldReaderWriter lldMachO lldYAML)
+    target_link_libraries(c3c optimized ${llvm_libs} c3c_wrappers lldCommon lldCore lldCOFF lldWASM lldMinGW lldELF lldDriver lldReaderWriter lldMachO lldYAML)
+endif()
 
 if (WIN32)
     if (CMAKE_C_COMPILER_ID STREQUAL "Clang" OR CMAKE_C_COMPILE_ID STREQUAL "GNU")

CMakeSettings.json

@@ -0,0 +1,15 @@
+{
+  "configurations": [
+    {
+      "name": "build",
+      "generator": "Ninja",
+      "configurationType": "Release",
+      "inheritEnvironments": [ "msvc_x64_x64" ],
+      "buildRoot": "${projectDir}\\out\\build\\${name}",
+      "installRoot": "${projectDir}\\out\\install\\${name}",
+      "cmakeCommandArgs": "-DLLVM_DIR=C:\\llvm\\llvm\\build\\lib\\cmake\\llvm -DCMAKE_CXX_FLAGS:STRING=\"${CMAKE_CXX_FLAGS} /J\"",
+      "buildCommandArgs": "-v",
+      "ctestCommandArgs": ""
+    }
+  ]
+}

src/build/build_options.c

@@ -6,7 +6,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
+#ifndef _MSC_VER
 #include <unistd.h>
+#endif
 #include <stdbool.h>
 #include <string.h>
 #include <utils/lib.h>

src/build/builder.c

@@ -1,8 +1,11 @@
 // Copyright (c) 2019 Christoffer Lerno. All rights reserved.
 // Use of this source code is governed by a LGPLv3.0
 // a copy of which can be found in the LICENSE file.
-
+#ifndef _MSC_VER
 #include <dirent.h>
+#else
+#include "utils/dirent.h"
+#endif
 #include "build_internal.h"
 #include "build_options.h"
 
@@ -93,6 +96,16 @@ static void update_build_target_from_options(BuildTarget *target, BuildOptions *
 	{
 		target->arch_os_target = options->arch_os_target_override;
 	}
+#ifndef _MSC_VER
+#define _MSC_VER 0
+#endif
+	else if (_MSC_VER)
+	{
+		// The current handling of ARCH_OS_TARGET_DEFAULT works on unix, but not on windows.
+		// to deal with this, simply default to x64-windows (unless using mingw).
+		// ARCH_OS_TARGET_DEFAULT could be handled in a more cross-platform manner later on.
+		target->arch_os_target = X64_WINDOWS;
+	}
 	if (options->pie != PIE_DEFAULT) target->pie = options->pie;
 	if (options->pic != PIC_DEFAULT) target->pic = options->pic;
 

src/build/project_creation.c

@@ -6,7 +6,9 @@
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
+#ifndef _MSC_VER
 #include <unistd.h>
+#endif
 #include <string.h>
 #include "project_creation.h"
 #include "build_options.h"

src/compiler/compiler.c

@@ -4,7 +4,9 @@
 
 #include "compiler_internal.h"
 #include "parser_internal.h"
+#ifndef _MSC_VER
 #include <unistd.h>
+#endif
 
 #define MAX_OUTPUT_FILES 1000000
 #define MAX_MODULES 100000
@@ -483,7 +485,7 @@ static void target_expand_source_names(BuildTarget *target)
 
 void compile_target(BuildOptions *options)
 {
-	init_default_build_target(&active_target, options, "a.out");
+	init_default_build_target(&active_target, options, DEFAULT_EXE);
 	compile();
 }
 

src/compiler/compiler_internal.h

@@ -30,6 +30,13 @@ typedef int32_t ScopeId;
 #define DEFAULT_EXE "a.out"
 #endif
 
+#if PLATFORM_WINDOWS
+#define DEFAULT_OBJ_FILE_EXT ".obj"
+#else
+#define DEFAULT_OBJ_FILE_EXT ".o"
+#endif
+
+
 typedef uint32_t SourceLoc;
 typedef struct
 {
@@ -554,9 +561,9 @@ typedef struct Decl_
 	SourceSpan span;
 	const char *external_name;
 	Ast *docs;
-	DeclKind decl_kind : 6;
-	Visibility visibility : 2;
-	ResolveStatus resolve_status : 2;
+	DeclKind decl_kind : 7;
+	Visibility visibility : 3;
+	ResolveStatus resolve_status : 3;
 	bool is_packed : 1;
 	bool is_opaque : 1;
 	bool needs_additional_pad : 1;

src/compiler/enums.h

@@ -295,7 +295,7 @@ typedef enum
 	TYPE_INFO_POINTER,
 } TypeInfoKind;
 
-typedef enum 
+typedef enum
 {
 	TOKEN_INVALID_TOKEN = 0,
 

src/compiler/linker.c

@@ -2,6 +2,10 @@
 
 #include <llvm/Config/llvm-config.h>  // for LLVM_VERSION_STRING
 
+#ifdef PLATFORM_WINDOWS
+#include "utils/find_msvc.h"
+#endif
+
 extern bool llvm_link_elf(const char **args, int arg_count, const char** error_string);
 extern bool llvm_link_macho(const char **args, int arg_count, const char** error_string);
 extern bool llvm_link_coff(const char **args, int arg_count, const char** error_string);
@@ -64,8 +68,19 @@ static void prepare_msys2_linker_flags(const char ***args, const char **files_to
 static bool link_exe(const char *output_file, const char **files_to_link, unsigned file_count)
 {
 	const char **args = NULL;
-	vec_add(args, "-o");
-	vec_add(args, output_file);
+#ifdef _MSC_VER
+	if (platform_target.os == OS_TYPE_WIN32)
+	{
+		vec_add(args, join_strings((const char* []) {"/out:", output_file}, 2));
+	}
+	else
+	{
+#endif
+		vec_add(args, "-o");
+		vec_add(args, output_file);
+#ifdef _MSC_VER
+	}
+#endif
 	VECEACH(active_target.link_args, i)
 	{
 		vec_add(args, active_target.link_args[i]);
@@ -78,16 +93,43 @@ static bool link_exe(const char *output_file, const char **files_to_link, unsign
 			// TODO: properly detect if llvm-lld is available
 			// TODO: check if running inside MSYS2, it could be done via getting MSYSTEM environment variable
 			// https://stackoverflow.com/questions/65527286/how-to-check-if-my-program-is-running-on-mingwor-msys-shell-or-on-cmd
-			if (!platform_target.x64.is_mingw64) return false;
-			if (NULL == getenv("MSYSTEM")) return false;
-			if (!strcmp(getenv("MSYSTEM"), "CLANG64") || !strcmp(getenv("MSYSTEM"), "MINGW64"))
+			if (NULL == getenv("MSYSTEM"))
 			{
-				prepare_msys2_linker_flags(&args, files_to_link, file_count);
+				// "native" windows
+
+
+				// find paths to library directories.
+				// ex:
+				// C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\BuildTools\\VC\\Tools\\MSVC\\14.28.29910\\lib\\x64
+				// C:\\Program Files (x86)\\Microsoft Visual Studio\\2019\\BuildTools\\VC\\Tools\\MSVC\\14.28.29910\\atlmfc\\lib\\x64
+				// C:\\Program Files (x86)\\Windows Kits\\10\\Lib\\10.0.19041.0\\ucrt\\x64
+				// C:\\Program Files (x86)\\Windows Kits\\10\\Lib\\10.0.19041.0\\um\\x64
+#ifdef _MSC_VER
+				PathPair msvc_paths = get_latest_available_vs_path();
+				PathPair windows_kit_paths = find_winkit_path();
+				vec_add(args, join_strings((const char* []) { "-libpath:C:", msvc_paths.first }, 2));
+				vec_add(args, join_strings((const char* []) { "-libpath:C:", msvc_paths.second }, 2));
+				vec_add(args, join_strings((const char* []) { "-libpath:C:", windows_kit_paths.first }, 2));
+				vec_add(args, join_strings((const char* []) { "-libpath:C:", windows_kit_paths.second }, 2));
+
+				vec_add(args, "-defaultlib:libcmt");
+				vec_add(args, "-nologo");
+				add_files(&args, files_to_link, file_count);
+#else
+				error_exit("ERROR - c3c must be compiled with MSVC to target x64-windows\n");
+#endif
 			}
 			else
 			{
-				return false;
-			}
+				if (!strcmp(getenv("MSYSTEM"), "CLANG64") || !strcmp(getenv("MSYSTEM"), "MINGW64"))
+				{
+					prepare_msys2_linker_flags(&args, files_to_link, file_count);
+				}
+				else
+				{
+					return false;
+				}
+			}			
 			break;
 		case OS_TYPE_MACOSX:
 			add_files(&args, files_to_link, file_count);

src/compiler/llvm_codegen_module.c

@@ -22,8 +22,7 @@ void gencontext_begin_module(GenContext *c)
 	}
 	const char *result = scratch_buffer_to_string();
 	c->ir_filename = strformat("%s.ll", result);
-	// TODO filename should depend on platform.
-	c->object_filename = strformat("%s.o", result);
+	c->object_filename = strformat("%s%s", result, DEFAULT_OBJ_FILE_EXT);
 
 	c->module = LLVMModuleCreateWithNameInContext(c->code_module->name->module, c->context);
 	c->machine = llvm_target_machine_create();

src/compiler/parse_expr.c

@@ -226,12 +226,14 @@ Expr *parse_cond(Context *context)
 	return decl_expr;
 }
 
-inline Expr* parse_expr(Context *context)
+// These used to be explicitly inlined, but that seems to lead to confusing MSVC linker errors.
+// They are probably still inlined by the compiler, though I haven't checked.
+Expr* parse_expr(Context *context)
 {
 	return parse_precedence(context, PREC_ASSIGNMENT);
 }
 
-inline Expr* parse_constant_expr(Context *context)
+Expr* parse_constant_expr(Context *context)
 {
 	return parse_precedence(context, PREC_TERNARY);
 }

src/compiler/sema_decls.c

@@ -989,6 +989,7 @@ static inline bool sema_analyse_func(Context *context, Decl *decl)
 {
 	DEBUG_LOG("----Analysing function %s", decl->name);
 	Type *func_type = sema_analyse_function_signature(context, &decl->func_decl.function_signature, true);
+	
 	decl->type = func_type;
 	if (!func_type) return decl_poison(decl);
 	if (decl->func_decl.type_parent)

src/compiler/sema_name_resolution.c

@@ -4,7 +4,10 @@
 
 #include "compiler_internal.h"
 
-
+#if defined(_MSC_VER)
+// This isn't standard apparently, so MSVC doesn't have it built in...
+typedef long long int ssize_t;
+#endif
 
 static inline bool matches_subpath(Path *path_to_check, Path *path_to_find)
 {

src/compiler/source_file.c

@@ -3,7 +3,13 @@
 // a copy of which can be found in the LICENSE file.
 
 #include <sys/stat.h>
+#ifdef _MSC_VER
+
+#define PATH_MAX 260
+
+#else
 #include <limits.h>
+#endif
 #include "compiler_internal.h"
 #include "../build/build_options.h"
 
@@ -23,7 +29,11 @@ File *source_file_load(const char *filename, bool *already_loaded)
 	if (already_loaded) *already_loaded = false;
 	if (!source_files.files) source_files.files = VECNEW(File *, LEXER_FILES_START_CAPACITY);
 
-	char *full_path = malloc_arena(PATH_MAX + 1);
+#ifdef _MSC_VER
+	char* full_path = malloc_arena(MAX_PATH + 1);
+#else
+	char* full_path = malloc_arena(PATH_MAX + 1);
+#endif
 	if (!realpath(filename, full_path))
 	{
 		error_exit("Failed to resolve %s", filename);

src/main.c

@@ -45,7 +45,6 @@ int main(int argc, const char *argv[])
 			UNREACHABLE
 	}
 
-
 	print_arena_status();
 	free_arena();
 	return 0;

src/utils/file_utils.c

@@ -6,18 +6,65 @@
 #include "common.h"
 #include "errors.h"
 #include "lib.h"
+
+#if PLATFORM_WINDOWS
+
+#include <windows.h>
+
+#endif
+
+#ifndef _MSC_VER
 #include <libgen.h>
+#include <unistd.h>
 #include <dirent.h>
 #include <limits.h>
-#include <unistd.h>
+#else
+#include "utils/dirent.h"
+#define PATH_MAX 260
+
+// dirname and basename on windows
+#include "win_dirname_basename.h"
+
+// copied from https://github.com/kindkaktus/libconfig/commit/d6222551c5c01c326abc99627e151d549e0f0958
+#ifndef S_ISDIR
+#define S_ISDIR(mode)  (((mode) & S_IFMT) == S_IFDIR)
+#endif
+// copied from https://stackoverflow.com/questions/11238918/s-isreg-macro-undefined
+#if !defined(S_ISREG) && defined(S_IFMT) && defined(S_IFREG)
+#define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
+#endif
+
+#endif
+
 #include <errno.h>
 #include "whereami.h"
 
 #if PLATFORM_WINDOWS
-#include <windows.h>
+
+
+/**
+ * remove C: drive prefix (C:, D:, etc.) from a path. THIS WON'T WORK WITH D:, ETC.
+ * If that is an issue, I think dirent will have to be replaced or the dirent
+ * port in use will have to be replaced.
+ */
+char* strip_drive_prefix(char* path) {
+	if ((*path == 'c' || *path == 'C') && path[1] == ':') {
+		return path + 2; // remove first two characters
+	}
+	else if (path[1] == ':' && (path[2] == '/' || path[2] == '\\')) { // I don't *think* a relative path can start with '[char]:/' ? right?
+		// nothing can be done about this currently
+		error_exit("Illegal path %s - absolute path must start with /, \\, c:, or C: (file a github issue if this is a problem)");
+	}
+	else {
+		// path is ok
+		return path;
+	}
+}
+
 #endif
 
 
+
 const char* expand_path(const char* path)
 {
 	if (path[0] == '~' && path[1] == '/')
@@ -147,7 +194,11 @@ void file_find_top_dir()
 
 void file_add_wildcard_files(const char ***files, const char *path, bool recursive)
 {
-	DIR *dir = opendir(path);
+#ifdef _MSC_VER
+	DIR *dir = opendir(strip_drive_prefix(path));
+#else
+	DIR* dir = opendir(path);
+#endif
 	bool path_ends_with_slash = path[strlen(path) - 1] == '/';
 	if (!dir)
 	{

src/utils/find_msvc.c

@@ -0,0 +1,79 @@
+#include "utils/common.h"
+#ifdef _MSC_VER
+
+#include "utils/find_msvc.h"
+
+#include <stdio.h>
+
+#include "utils/dirent.h"
+
+#define MSVC_BASE_PATH "/Program Files (x86)/Microsoft Visual Studio/"
+#define WINKIT_BASE_PATH "/Program Files (x86)/Windows Kits/"
+
+
+int is_numeric(const struct dirent* ent) {
+    return atoi(ent->d_name); // don't use this function if you expect a file named "0" ?
+}
+
+char* get_highest_ver(char* directory, int (*filter)(const struct dirent*)) {
+    struct dirent** files;
+    int num_files = scandir(directory, &files, filter, versionsort);
+    if (num_files < 0) {
+        error_exit("ERROR - Failed to autodetect MSVC libpaths\n");
+    }
+    char* path_ret = (char*)malloc(260);
+    strcpy_s(path_ret, 260, files[num_files - 1]->d_name);
+    for (int i = 0; i < num_files; i++) free(files[i]);
+    free(files);
+    return path_ret;
+}
+
+/**
+ * @returns PathPair containing paths to .../MSVC/[version]/lib/x64 and .../MSVC/[v]/atlmfc/lib/x64
+ */
+PathPair get_latest_available_vs_path() {
+    char ver_name[16] = "";
+
+    char* highest_ver = get_highest_ver(MSVC_BASE_PATH, is_numeric);
+    strncpy_s(ver_name, 16, highest_ver, 4);
+    free(highest_ver);
+
+    char newpath[260];
+    snprintf(newpath, 260, "%s%s/BuildTools/VC/Tools/MSVC/", MSVC_BASE_PATH, ver_name);
+
+    highest_ver = get_highest_ver(newpath, NULL);
+    strcat_s(newpath, 260, highest_ver);
+    free(highest_ver);
+
+    PathPair ret = { 0 };
+    snprintf(ret.first, 260, "%s/lib/x64", newpath);
+    snprintf(ret.second, 260, "%s/atlmfc/lib/x64", newpath);
+
+    return ret;
+}
+
+/**
+ * @returns PathPair containing paths to /Program Files (x86)/Windows Kits/[version]/Lib/[version]/ucrt/x64 and .../[version]/um/x64
+ */
+PathPair find_winkit_path() {
+    // windows version
+    char win_ver_major[16] = "";
+    char* highest_ver = get_highest_ver(WINKIT_BASE_PATH, is_numeric);
+    strcpy_s(win_ver_major, 16, highest_ver);
+    free(highest_ver);
+
+    // windows kit version? or something
+    char newpath[260] = "";
+    sprintf_s(newpath, 260, "%s%s/Lib/", WINKIT_BASE_PATH, win_ver_major);
+    highest_ver = get_highest_ver(newpath, NULL);
+    strcat_s(newpath, 260, highest_ver);
+    free(highest_ver);
+
+    PathPair ret = { 0 };
+    snprintf(ret.first, 260, "%s/ucrt/x64", newpath);
+    snprintf(ret.second, 260, "%s/um/x64", newpath);
+
+    return ret;
+}
+
+#endif //defined(_MSC_VER)

src/utils/find_msvc.h

@@ -0,0 +1,9 @@
+#pragma once
+
+typedef struct {
+    char first[260];
+    char second[260];
+} PathPair;
+
+PathPair get_latest_available_vs_path();
+PathPair find_winkit_path();

src/utils/stringutils.c

@@ -104,6 +104,21 @@ int vasnprintf(char **strp, const char *fmt, va_list args)
 	return res;
 }
 
+int vasprintf(char** ret, const char* fmt, va_list args) {
+	int length = _vsnprintf(NULL, 0, fmt, args);
+	if (length < 0) { // check if _vsnprintf failed
+		return -1;
+	}
+	*ret = malloc(length + 1);
+	if (!*ret) { // check if malloc failed
+		return -1;
+	}
+	// Write String 
+	_vsnprintf(*ret, length + 1, fmt, args);
+	(*ret)[length] = '\0'; // make sure there is a null terminator
+	return length;
+}
+
 char *strndup(const char *s, size_t n)
 {
 	n = strnlen(s, n);

src/utils/vmem.c

@@ -2,13 +2,14 @@
 // Use of this source code is governed by a LGPLv3.0
 // a copy of which can be found in the LICENSE file.
 
+
 #include "vmem.h"
 
 #if PLATFORM_POSIX
 #include <sys/mman.h>
 #endif
 
-#if PLATFORM_WINDOWS
+#if defined(WIN32)
 #include <Windows.h>
 #define COMMIT_PAGE_SIZE 0x10000
 #endif

src/utils/whereami.c

@@ -4,6 +4,10 @@
 
 // Code based off Gregory Pakosz's whereami.
 
+#if defined(WIN32)
+#include <windows.h>
+#endif
+
 #include "whereami.h"
 
 #include <stdlib.h>
@@ -32,7 +36,6 @@
 #pragma warning(push, 3)
 #endif
 
-#include <windows.h>
 #include <intrin.h>
 
 #if defined(_MSC_VER)

src/utils/win_dirname_basename.h

@@ -0,0 +1,64 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+// TODO I made these super quickly so they probably have some bugs from cases I didn't think of.
+// A better implementation of these functions may be necessary.
+
+char* basename(char* path)
+{
+	size_t len = strlen(path);
+	size_t lastSlash = 0;
+	for (size_t i = len - 2; i > 0; i--)
+	{
+		if (path[i] == '\\' || path[i] == '/')
+		{
+			if (i == len)
+			{
+				continue;
+			}
+			lastSlash = i;
+			break;
+		}
+		if (i == 0)
+		{
+			// according to `man 3 basename` if there is no /, the original path should be returned
+			char* newStr = (char*)malloc(len);
+			strcpy(newStr, path);
+			return newStr;
+		}
+	}
+	size_t newSize = len - lastSlash - 1;
+	char* newStr = (char*)malloc(newSize);
+	strncpy(newStr, path + lastSlash + 1, newSize);
+	return newStr;
+}
+
+char* dirname(char* path)
+{
+	size_t len = strlen(path);
+	size_t lastSlash = 0;
+	for (size_t i = len - 2; i > 0; i--)
+	{
+		if (path[i] == '\\' || path[i] == '/')
+		{
+			if (i == len)
+			{
+				continue;
+			}
+			lastSlash = i;
+			break;
+		}
+		if (i == 0)
+		{
+			// according to `man 3 basename` if there is no /, "." should be returned
+			char* newStr = (char*)malloc(2);
+			strcpy(newStr, ".");
+			return newStr;
+		}
+	}
+	// size_t newSize = len - lastSlash - 1;
+	char* newStr = (char*)malloc(lastSlash);
+	strncpy(newStr, path, lastSlash);
+	return newStr;
+}

windows_build.md

@@ -0,0 +1,29 @@
+# Building and using C3C on windows
+
+Windows support in C3C is currently experimental and unstable. It has many limitations and likely has bugs. With that aside, here's how you can build and use it:
+
+## Compiling LLVM
+
+First, follow the steps outlined here to set up and compile LLVM:
+
+https://llvm.org/docs/GettingStartedVS.html
+
+When running cmake, use the following options to enable all of the libraries needed by C3C:
+
+```
+cmake .. -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_TARGETS_TO_BUILD="ARM;AArch64;RISCV;WebAssembly;X86" -Thost=x64
+```
+
+## Compiling C3C
+
+Clone the C3C github repository and open its directory in visual studio. VS should detect the CMake configuration, allowing you to simply use Build -> Build All to compile C3C. A `c3c.exe` will be placed in `out/build/build`.
+
+## Using C3C on Windows
+
+At this point, you should be able to use C3C normally. For example:
+
+```
+/c3c/out/build/build/c3c.exe compile ./hello_world.c3c
+```
+
+Note that on windows, linker arguments passed through c3c using `-z` will need to be of the format expected by `lld-link`, which uses MSVC `link.exe`-format arguments rather than the GCC/Clang format.