filesystem: Added SDL_GetExeName().

core/unix had a more-limited copy of filesystem/unix's implementation, called
SDL_GetExeName(). Replace that with a real implementation in filesystem, and
allow each platform to implement it as appropriate.

Implemented for Unix and Windows; most implementations are currently FIXME
stubs at the moment.

Reference Issue #15692.

(cherry picked from commit 7d29ce8e31)

src/core/linux/SDL_fcitx.c

@@ -54,6 +54,7 @@ typedef struct FcitxClient
 
 static FcitxClient fcitx_client;
 
+// !!! FIXME: should this just be dumped for src/core/unix's SDL_GetAppID()?
 static const char *GetAppName(void)
 {
     const char *exe_name = SDL_GetExeName();

src/core/unix/SDL_appid.c

@@ -24,39 +24,6 @@
 #include "SDL_appid.h"
 #include <unistd.h>
 
-const char *SDL_GetExeName(void)
-{
-    static const char *proc_name = NULL;
-
-    // TODO: Use a fallback if BSD has no mounted procfs (OpenBSD has no procfs at all)
-    if (!proc_name) {
-#if defined(SDL_PLATFORM_LINUX) || defined(SDL_PLATFORM_FREEBSD) || defined (SDL_PLATFORM_NETBSD) || defined(SDL_PLATFORM_HURD)
-        static char linkfile[1024];
-        int linksize;
-
-#if defined(SDL_PLATFORM_LINUX) || defined(SDL_PLATFORM_HURD)
-        const char *proc_path = "/proc/self/exe";
-#elif defined(SDL_PLATFORM_FREEBSD)
-        const char *proc_path = "/proc/curproc/file";
-#elif defined(SDL_PLATFORM_NETBSD)
-        const char *proc_path = "/proc/curproc/exe";
-#endif
-        linksize = readlink(proc_path, linkfile, sizeof(linkfile) - 1);
-        if (linksize > 0) {
-            linkfile[linksize] = '\0';
-            proc_name = SDL_strrchr(linkfile, '/');
-            if (proc_name) {
-                ++proc_name;
-            } else {
-                proc_name = linkfile;
-            }
-        }
-#endif
-    }
-
-    return proc_name;
-}
-
 const char *SDL_GetAppID(void)
 {
     const char *id_str = SDL_GetAppMetadataProperty(SDL_PROP_APP_METADATA_IDENTIFIER_STRING);
@@ -73,3 +40,4 @@ const char *SDL_GetAppID(void)
 
     return id_str;
 }
+

src/core/unix/SDL_appid.h

@@ -24,7 +24,6 @@ freely, subject to the following restrictions:
 #ifndef SDL_appid_h_
 #define SDL_appid_h_
 
-extern const char *SDL_GetExeName(void);
 extern const char *SDL_GetAppID(void);
 
 #endif // SDL_appid_h_

src/core/windows/SDL_windows.c

@@ -730,4 +730,42 @@ const char *WIN_CheckDefaultArgcArgv(int *pargc, char ***pargv, void **pallocate
     return NULL;  // no error string.
 }
 
+char *WIN_GetModulePath(HMODULE handle)
+{
+    DWORD buflen = 128;
+    WCHAR *path = NULL;
+    DWORD len = 0;
+
+    while (true) {
+        void *ptr = SDL_realloc(path, buflen * sizeof(WCHAR));
+        if (!ptr) {
+            SDL_free(path);
+            return NULL;
+        }
+
+        path = (WCHAR *)ptr;
+
+        len = GetModuleFileNameW(handle, path, buflen);
+        // if it truncated, then len >= buflen - 1
+        // if there was enough room (or failure), len < buflen - 1
+        if (len < (buflen - 1)) {
+            break;
+        }
+
+        // buffer too small? Try again.
+        buflen *= 2;
+    }
+
+    char *retval = NULL;
+    if (len == 0) {
+        WIN_SetError("Couldn't locate module");
+    } else {
+        retval = WIN_StringToUTF8W(path);
+    }
+
+    SDL_free(path);
+
+    return retval;
+}
+
 #endif // defined(SDL_PLATFORM_WINDOWS)

src/core/windows/SDL_windows.h

@@ -213,7 +213,10 @@ extern SDL_AudioFormat SDL_WaveFormatExToSDLFormat(WAVEFORMATEX *waveformat);
 extern int WIN_WideCharToMultiByte(UINT CodePage, DWORD dwFlags, LPCWCH lpWideCharStr, int cchWideChar, LPSTR lpMultiByteStr, int cbMultiByte, LPCCH lpDefaultChar, LPBOOL lpUsedDefaultChar);
 
 // parse out command lines from OS if argv is NULL, otherwise pass through unchanged. `*pallocated` must be HeapFree'd by caller if not NULL on successful return. Returns NULL on success, error string on problems.
-const char *WIN_CheckDefaultArgcArgv(int *pargc, char ***pargv, void **pallocated);
+extern const char *WIN_CheckDefaultArgcArgv(int *pargc, char ***pargv, void **pallocated);
+
+// Does all the win32 tapdancing to make GetModuleFileName work. Returns a SDL_malloc'd UTF-8 string, or NULL on failure.
+extern char *WIN_GetModulePath(HMODULE handle);
 
 // Ends C function definitions when using C++
 #ifdef __cplusplus