Added DLL loading capability in windows to the std lib. Ensure that t…

src/link.cpp

@@ -11,6 +11,11 @@
 #include "codegen.hpp"
 #include "analyze.hpp"
 
+#ifdef ZIG_OS_WINDOWS
+#define WIN32_LEAN_AND_MEAN
+    #include <Windows.h>
+#endif
+
 struct LinkJob {
     CodeGen *codegen;
     Buf out_file;
@@ -488,18 +493,28 @@ static void construct_linker_job_coff(LinkJob *lj) {
             if (lj->codegen->zig_target.env_type == ZigLLVM_GNU) {
                 Buf *arg = buf_sprintf("-l%s", buf_ptr(link_lib->name));
                 lj->args.append(buf_ptr(arg));
-            }
-            else {
+            } else {
                 lj->args.append(buf_ptr(link_lib->name));
             }
         } else {
             buf_resize(def_contents, 0);
             buf_appendf(def_contents, "LIBRARY %s\nEXPORTS\n", buf_ptr(link_lib->name));
+#ifdef ZIG_OS_WINDOWS
+            Buf* dll_name = buf_create_from_buf(link_lib->name);
+            buf_append_str(dll_name, ".dll");
+            HMODULE hmod = GetModuleHandle(buf_ptr(dll_name));
+            assert(hmod);
             for (size_t exp_i = 0; exp_i < link_lib->symbols.length; exp_i += 1) {
                 Buf *symbol_name = link_lib->symbols.at(exp_i);
+                FARPROC symbol_addr = GetProcAddress(hmod, buf_ptr(symbol_name));
+                if (symbol_addr == NULL) {
+                    fprintf(stderr, "error: extern symbol: %s does not exist in: %s.\n", buf_ptr(symbol_name), buf_ptr(dll_name));
+                    exit(1);
+                }
                 buf_appendf(def_contents, "%s\n", buf_ptr(symbol_name));
             }
             buf_appendf(def_contents, "\n");
+#endif
 
             Buf *def_path = buf_alloc();
             os_path_join(g->cache_dir, buf_sprintf("%s.def", buf_ptr(link_lib->name)), def_path);

std/os/index.zig

@@ -31,6 +31,8 @@ pub const windowsWaitSingle = windows_util.windowsWaitSingle;
 pub const windowsWrite = windows_util.windowsWrite;
 pub const windowsIsCygwinPty = windows_util.windowsIsCygwinPty;
 pub const windowsOpen = windows_util.windowsOpen;
+pub const windowsLoadDll = windows_util.windowsLoadDll;
+pub const windowsUnloadDll = windows_util.windowsUnloadDll; 
 pub const createWindowsEnvBlock = windows_util.createWindowsEnvBlock;
 
 pub const FileHandle = if (is_windows) windows.HANDLE else i32;

std/os/windows/index.zig

@@ -84,6 +84,11 @@ pub extern "kernel32" stdcallcc fn WriteFile(in_hFile: HANDLE, in_lpBuffer: &con
     in_nNumberOfBytesToWrite: DWORD, out_lpNumberOfBytesWritten: ?&DWORD,
     in_out_lpOverlapped: ?&OVERLAPPED) -> BOOL;
 
+//TODO: call unicode versions instead of relying on ANSI code page
+pub extern "kernel32" stdcallcc fn LoadLibraryA(lpLibFileName: LPCSTR) -> ?HMODULE;
+
+pub extern "kernel32" stdcallcc fn FreeLibrary(hModule: HMODULE) -> BOOL;   
+
 pub extern "user32" stdcallcc fn MessageBoxA(hWnd: ?HANDLE, lpText: ?LPCTSTR, lpCaption: ?LPCTSTR, uType: UINT) -> c_int;
 
 pub const PROV_RSA_FULL = 1;
@@ -97,6 +102,7 @@ pub const FLOAT = f32;
 pub const HANDLE = &c_void;
 pub const HCRYPTPROV = ULONG_PTR;
 pub const HINSTANCE = &@OpaqueType();
+pub const HMODULE = &@OpaqueType();
 pub const INT = c_int;
 pub const LPBYTE = &BYTE;
 pub const LPCH = &CHAR;

std/os/windows/util.zig

@@ -4,6 +4,7 @@ const windows = std.os.windows;
 const assert = std.debug.assert;
 const mem = std.mem;
 const BufMap = std.BufMap;
+const cstr = std.cstr;
 
 error WaitAbandoned;
 error WaitTimeOut;
@@ -149,3 +150,19 @@ pub fn createWindowsEnvBlock(allocator: &mem.Allocator, env_map: &const BufMap)
     result[i] = 0;
     return result;
 }
+
+error DllNotFound;
+pub fn windowsLoadDll(allocator: &mem.Allocator, dll_path: []const u8) -> %windows.HMODULE {
+    const padded_buff = %return cstr.addNullByte(allocator, dll_path);
+    defer allocator.free(padded_buff);
+    const rc = windows.LoadLibraryA(padded_buff.ptr);
+    if(rc == null) { 
+        return error.DllNotFound;
+    } else {
+        return @ptrCast(windows.HMODULE, rc);
+    }
+}
+
+pub fn windowsUnloadDll(hModule: windows.HMODULE) {
+    assert(windows.FreeLibrary(hModule)!= 0);
+}

test/compare_output.zig

@@ -444,4 +444,18 @@ pub fn addCases(cases: &tests.CompareOutputContext) {
 
         tc
     });
+
+    cases.add("windowsLoadDll failure",
+        \\const std = @import("std");
+        \\const debug = std.debug;
+        \\const os = std.os;
+        \\const win = std.os.windows;
+        \\const allocator = std.debug.global_allocator;
+        \\pub fn main() -> %void {
+        \\    const handle = os.windowsLoadDll(allocator, "asdf.dll") %%  |err| {
+        \\        debug.warn("{}: {}", @errorName(err), OpenGLDLL);
+        \\        return;
+        \\    };
+        \\}
+    , "DllNotFound: asdf.dll\n");
 }