[rcore][android] Replace `android_fopen()` with linker `--wrap=fopen` (#5605)

* ANDROID: replace android_fopen with linker --wrap=fopen

* ANDROID: add --wrap=fopen linker flag to src/Makefile

src/CMakeLists.txt

@@ -75,6 +75,12 @@ if (${PLATFORM} MATCHES "Web")
     endif()
 endif()
 
+if (${PLATFORM} MATCHES "Android")
+    # Wrap fopen at link time so all code (including third-party libs) goes
+    # through __wrap_fopen, which handles Android APK asset loading
+    target_link_options(raylib INTERFACE -Wl,--wrap=fopen)
+endif()
+
 set_target_properties(raylib PROPERTIES
                       PUBLIC_HEADER "${raylib_public_headers}"
                       VERSION ${PROJECT_VERSION}

src/Makefile

@@ -614,6 +614,9 @@ ifeq ($(TARGET_PLATFORM),PLATFORM_ANDROID)
     LDFLAGS += -Lsrc
     # Avoid unresolved symbol pointing to external main()
     LDFLAGS += -Wl,-undefined,dynamic_lookup
+    # Wrap fopen at link time so all code (including third-party libs) goes
+    # through __wrap_fopen, which handles Android APK asset loading
+    LDFLAGS += -Wl,--wrap=fopen
 endif
 
 # Define libraries required on linking: LDLIBS

src/platforms/rcore_android.c

@@ -275,12 +275,12 @@ static int android_write(void *cookie, const char *buf, int size);
 static fpos_t android_seek(void *cookie, fpos_t offset, int whence);
 static int android_close(void *cookie);
 
-FILE *android_fopen(const char *fileName, const char *mode); // Replacement for fopen() -> Read-only!
+FILE *__real_fopen(const char *fileName, const char *mode); // Real fopen, provided by the linker (--wrap=fopen)
+FILE *__wrap_fopen(const char *fileName, const char *mode); // Replacement for fopen()
+
 FILE *funopen(const void *cookie, int (*readfn)(void *, char *, int), int (*writefn)(void *, const char *, int),
               fpos_t (*seekfn)(void *, fpos_t, int), int (*closefn)(void *));
 
-#define fopen(name, mode) android_fopen(name, mode)
-
 //----------------------------------------------------------------------------------
 // Module Functions Declaration
 //----------------------------------------------------------------------------------
@@ -1524,25 +1524,20 @@ static void SetupFramebuffer(int width, int height)
     }
 }
 
-// Replacement for fopen()
+// Replacement for fopen(), used as linker wrap entry point (-Wl,--wrap=fopen)
 // REF: https://developer.android.com/ndk/reference/group/asset
-FILE *android_fopen(const char *fileName, const char *mode)
+FILE *__wrap_fopen(const char *fileName, const char *mode)
 {
     FILE *file = NULL;
-    
+
+    // NOTE: AAsset provides access to read-only asset, write operations use regular fopen
     if (mode[0] == 'w')
     {
-        // NOTE: fopen() is mapped to android_fopen() that only grants read access to
-        // assets directory through AAssetManager but it could be required to write data
-        // using the standard stdio FILE access functions
-        // REF: https://stackoverflow.com/questions/11294487/android-writing-saving-files-from-native-code-only
-        #undef fopen
-        file = fopen(TextFormat("%s/%s", platform.app->activity->internalDataPath, fileName), mode);
-        #define fopen(name, mode) android_fopen(name, mode)
+        file = __real_fopen(TextFormat("%s/%s", platform.app->activity->internalDataPath, fileName), mode);
+        if (file == NULL) file = __real_fopen(fileName, mode);
     }
     else
     {
-        // NOTE: AAsset provides access to read-only asset
         AAsset *asset = AAssetManager_open(platform.app->activity->assetManager, fileName, AASSET_MODE_UNKNOWN);
 
         if (asset != NULL)
@@ -1552,14 +1547,12 @@ FILE *android_fopen(const char *fileName, const char *mode)
         }
         else
         {
-            #undef fopen
             // Just do a regular open if file is not found in the assets
-            file = fopen(TextFormat("%s/%s", platform.app->activity->internalDataPath, fileName), mode);
-            if (file == NULL) file = fopen(fileName, mode);
-            #define fopen(name, mode) android_fopen(name, mode)
+            file = __real_fopen(TextFormat("%s/%s", platform.app->activity->internalDataPath, fileName), mode);
+            if (file == NULL) file = __real_fopen(fileName, mode);
         }
     }
-    
+
     return file;
 }
 

src/raudio.c

@@ -180,11 +180,6 @@ typedef struct tagBITMAPINFOHEADER {
 #include <stdio.h>                      // Required for: FILE, fopen(), fclose(), fread()
 #include <string.h>                     // Required for: strcmp() [Used in IsFileExtension(), LoadWaveFromMemory(), LoadMusicStreamFromMemory()]
 
-#if defined(PLATFORM_ANDROID)
-    FILE *android_fopen(const char *fileName, const char *mode);
-    #define fopen(name, mode) android_fopen(name, mode)
-#endif
-
 #if defined(RAUDIO_STANDALONE)
     #ifndef TRACELOG
         #define TRACELOG(level, ...)    printf(__VA_ARGS__)