fix: can't get dlopen()

.gitignore

@@ -43,4 +43,7 @@ subprojects/Vulkan-Headers-*/
 #GNU Global Metadata
 **/GPATH
 **/GRTAGS
-**/GTAGS
+**/GTAGS
+
+# clang cache
+.cache

src/real_dlsym.cpp

@@ -6,37 +6,57 @@
 
 #include <dlfcn.h>
 #include <stdio.h>
+#include <stdbool.h>
 #include <stdlib.h>
 #include "real_dlsym.h"
 #include "elfhacks.h"
 
-void *(*__dlopen)(const char *, int) = nullptr;
-void *(*__dlsym)(void *, const char *) = nullptr;
-static bool print_dlopen = getenv("IMGOVERLAY_DEBUG_DLOPEN") != nullptr;
-static bool print_dlsym = getenv("IMGOVERLAY_DEBUG_DLSYM") != nullptr;
+void *(*__dlopen)(const char *, int) = NULL;
+void *(*__dlsym)(void *, const char *) = NULL;
+char *(*__dlerror)(void) = NULL;
+static bool print_dlopen;
+static bool print_dlsym;
 
-void get_real_functions()
+static void get_real_functions()
 {
     eh_obj_t libdl;
+    int ret;
 
-    if (eh_find_obj(&libdl, "*libdl.so*")) {
-        if (eh_find_obj(&libdl, "*libc.so*")) {
-            fprintf(stderr, "can't get libdl.so and libc.so\n");
-            exit(1);
-        }
-    }
-
-    if (eh_find_sym(&libdl, "dlopen", (void **) &__dlopen)) {
-        fprintf(stderr, "can't get dlopen()\n");
-        exit(1);
+    const char* libs[] = {
+#if defined(__GLIBC__)
+        "*libdl.so*",
+#endif
+        "*libc.so*",
+        "*libc.*.so*",
+        "*ld-musl-*.so*",
+    };
+
+    print_dlopen = getenv("IMGOVERLAY_DEBUG_DLOPEN") != NULL;
+    print_dlsym = getenv("IMGOVERLAY_DEBUG_DLSYM") != NULL;
+
+    for (size_t i = 0; i < sizeof(libs) / sizeof(*libs); i++)
+    {
+        ret = eh_find_obj(&libdl, libs[i]);
+        if (ret)
+            continue;
+
+        eh_find_sym(&libdl, "dlopen", (void **) &__dlopen);
+        eh_find_sym(&libdl, "dlsym", (void **) &__dlsym);
+        eh_find_sym(&libdl, "dlerror", (void **) &__dlerror);
+        eh_destroy_obj(&libdl);
+
+        if (__dlopen && __dlsym && __dlerror)
+            break;
+        __dlopen = NULL;
+        __dlsym = NULL;
+        __dlerror = NULL;
     }
 
-    if (eh_find_sym(&libdl, "dlsym", (void **) &__dlsym)) {
-        fprintf(stderr, "can't get dlsym()\n");
-        exit(1);
+    if (!__dlopen && !__dlsym && !__dlerror)
+    {
+        fprintf(stderr, "IMGOVERLAY: Can't get dlopen(), dlsym() and dlerror()\n");
+        exit(ret ? ret : 1);
     }
-
-    eh_destroy_obj(&libdl);
 }
 
 /**
@@ -45,7 +65,7 @@ void get_real_functions()
  */
 void *real_dlopen(const char *filename, int flag)
 {
-    if (__dlopen == nullptr)
+    if (__dlopen == NULL)
         get_real_functions();
 
     void *result = __dlopen(filename, flag);
@@ -76,7 +96,7 @@ void *real_dlopen(const char *filename, int flag)
  */
 void *real_dlsym(void *handle, const char *symbol)
 {
-    if (__dlsym == nullptr)
+    if (__dlsym == NULL)
         get_real_functions();
 
     void *result = __dlsym(handle, symbol);
@@ -87,33 +107,13 @@ void *real_dlsym(void *handle, const char *symbol)
     return result;
 }
 
-void* get_proc_address(const char* name) {
-    void (*func)() = (void (*)())real_dlsym(RTLD_NEXT, name);
-    return (void*)func;
-}
-
-#ifdef HOOK_DLSYM
-EXPORT_C_(void *) imgoverlay_find_glx_ptr(const char *name);
-EXPORT_C_(void *) imgoverlay_find_egl_ptr(const char *name);
-
-EXPORT_C_(void*) dlsym(void * handle, const char * name)
+char* real_dlerror(void)
 {
-    void* func = nullptr;
-#ifdef HAVE_X11
-    func = imgoverlay_find_glx_ptr(name);
-    if (func) {
-        //fprintf(stderr,"%s: local: %s\n",  __func__ , name);
-        return func;
-    }
-#endif
-
-    func = imgoverlay_find_egl_ptr(name);
-    if (func) {
-        //fprintf(stderr,"%s: local: %s\n",  __func__ , name);
-        return func;
-    }
-
-    //fprintf(stderr,"%s: foreign: %s\n",  __func__ , name);
-    return real_dlsym(handle, name);
+    if (__dlerror == NULL)
+        get_real_functions();
+    return __dlerror();
 }
-#endif
+
+void* get_proc_address(const char* name) {
+    return real_dlsym(RTLD_NEXT, name);
+}