egl: simplify client/platform extension handling

For GLVND reasons the client/platform extensions strings should be
split. While in the non GLVND case they're one big string.

Currently we handle this distinction at run-time for not obvious reason.
Adding additional code and complexity.

Swap those with a few well placed #if USE_LIBGLVND guards.

As a side result this removes a minor memory leak due to the
concatenation in the non GLVND case.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4491>

src/egl/main/eglapi.c

@@ -692,13 +692,11 @@ eglQueryString(EGLDisplay dpy, EGLint name)
    _EGLDisplay *disp;
    _EGLDriver *drv;
 
+#if !USE_LIBGLVND
    if (dpy == EGL_NO_DISPLAY && name == EGL_EXTENSIONS) {
-      const char *ret = _eglGetClientExtensionString();
-      if (ret != NULL)
-         RETURN_EGL_SUCCESS(NULL, ret);
-      else
-         RETURN_EGL_ERROR(NULL, EGL_BAD_ALLOC, NULL);
+      RETURN_EGL_SUCCESS(NULL, _eglGlobal.ClientExtensionString);
    }
+#endif
 
    disp = _eglLockDisplay(dpy);
    _EGL_FUNC_START(disp, EGL_OBJECT_DISPLAY_KHR, NULL, NULL);

src/egl/main/eglglobals.c

@@ -62,16 +62,27 @@ struct _egl_global _eglGlobal =
       _eglFiniDisplay,
    },
 
+#if USE_LIBGLVND
    .ClientOnlyExtensionString =
+#else
+   .ClientExtensionString =
+#endif
    "EGL_EXT_client_extensions"
    " EGL_EXT_device_base"
    " EGL_EXT_device_enumeration"
    " EGL_EXT_device_query"
    " EGL_EXT_platform_base"
    " EGL_KHR_client_get_all_proc_addresses"
-   " EGL_KHR_debug",
+   " EGL_KHR_debug"
 
+#if USE_LIBGLVND
+   ,
    .PlatformExtensionString =
+#else
+   " "
+#endif
+
+   "EGL_EXT_platform_device"
 #ifdef HAVE_WAYLAND_PLATFORM
    " EGL_EXT_platform_wayland"
 #endif
@@ -84,11 +95,8 @@ struct _egl_global _eglGlobal =
 #ifdef HAVE_SURFACELESS_PLATFORM
    " EGL_MESA_platform_surfaceless"
 #endif
-   " EGL_EXT_platform_device"
    "",
 
-   .ClientExtensionString = NULL,
-
    .debugCallback = NULL,
    .debugTypesEnabled = _EGL_DEBUG_BIT_CRITICAL | _EGL_DEBUG_BIT_ERROR,
 };
@@ -123,40 +131,6 @@ _eglAddAtExitCall(void (*func)(void))
    }
 }
 
-const char *
-_eglGetClientExtensionString(void)
-{
-   const char *ret;
-
-   mtx_lock(_eglGlobal.Mutex);
-
-   if (_eglGlobal.ClientExtensionString == NULL) {
-      size_t clientLen = strlen(_eglGlobal.ClientOnlyExtensionString);
-      size_t platformLen = strlen(_eglGlobal.PlatformExtensionString);
-
-      _eglGlobal.ClientExtensionString = (char *) malloc(clientLen + platformLen + 1);
-      if (_eglGlobal.ClientExtensionString != NULL) {
-         char *ptr = _eglGlobal.ClientExtensionString;
-
-         memcpy(ptr, _eglGlobal.ClientOnlyExtensionString, clientLen);
-         ptr += clientLen;
-
-         if (platformLen > 0) {
-            // Note that if PlatformExtensionString is not empty, then it will
-            // already have a leading space.
-            assert(_eglGlobal.PlatformExtensionString[0] == ' ');
-            memcpy(ptr, _eglGlobal.PlatformExtensionString, platformLen);
-            ptr += platformLen;
-         }
-         *ptr = '\0';
-      }
-   }
-   ret = _eglGlobal.ClientExtensionString;
-
-   mtx_unlock(_eglGlobal.Mutex);
-   return ret;
-}
-
 EGLBoolean
 _eglPointerIsDereferencable(void *p)
 {

src/egl/main/eglglobals.h

@@ -61,13 +61,15 @@ struct _egl_global
 
    /*
     * Under libglvnd, the client extension string has to be split into two
-    * strings, one for platform extensions, and one for everything else. So,
-    * define separate strings for them. _eglGetClientExtensionString will
-    * concatenate them together for a non-libglvnd build.
+    * strings, one for platform extensions, and one for everything else.
+    * For a non-glvnd build create a concatenated one.
     */
+#if USE_LIBGLVND
    const char *ClientOnlyExtensionString;
    const char *PlatformExtensionString;
-   char *ClientExtensionString;
+#else
+   const char *ClientExtensionString;
+#endif
 
    EGLDEBUGPROCKHR debugCallback;
    unsigned int debugTypesEnabled;
@@ -86,9 +88,6 @@ static inline unsigned int DebugBitFromType(EGLenum type)
    return (1 << (type - EGL_DEBUG_MSG_CRITICAL_KHR));
 }
 
-extern const char *
-_eglGetClientExtensionString(void);
-
 /**
  * Perform validity checks on a generic pointer.
  */

src/egl/main/eglglvnd.c

@@ -24,15 +24,8 @@ __eglGLVNDQueryString(EGLDisplay dpy, EGLenum name)
 static const char *
 __eglGLVNDGetVendorString(int name)
 {
-   if (name == __EGL_VENDOR_STRING_PLATFORM_EXTENSIONS) {
-      const char *str = _eglGlobal.PlatformExtensionString;
-      // The platform extension string may have a leading space. If it does,
-      // then skip over it.
-      while (*str == ' ') {
-         str++;
-      }
-      return str;
-   }
+   if (name == __EGL_VENDOR_STRING_PLATFORM_EXTENSIONS)
+      return _eglGlobal.PlatformExtensionString;
 
    return NULL;
 }