Revert "glx: convert glx_config_create_list to one big calloc"

This reverts commit 35fc7bdf0e6ad6547e39099e7060a3d89539b56d.

Unfortunately mentioned commit introduced a memory leak because
`driwindowsMapConfigs` and `createDriMode` functions allocate
small memory portions for each element:
 21,576 (232 direct, 21,344 indirect) bytes in 1 blocks are definitely lost in loss record 1,411 of 1,414
    at 0x483A7F3: malloc (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
    by 0x5D4AA09: createDriMode (dri_common.c:291)
    by 0x5D4ABF5: driConvertConfigs (dri_common.c:310)
    by 0x5D58414: dri3_create_screen (dri3_glx.c:945)
    by 0x5D39829: AllocAndFetchScreenConfigs (glxext.c:815)
    by 0x5D39C57: __glXInitialize (glxext.c:941)
    by 0x5D3290A: GetGLXPrivScreenConfig (glxcmds.c:174)
    by 0x5D34F38: glXQueryExtensionsString (glxcmds.c:1307)
    by 0x4F83038: glXQueryExtensionsString (in /usr/local/lib/libGL.so.1.7.0)
    by 0x4F2EA6B: ??? (in /usr/lib/x86_64-linux-gnu/libwaffle-1.so.0.6.0)
    by 0x4F2A0D7: waffle_display_connect (in /usr/lib/x86_64-linux-gnu/libwaffle-1.so.0.6.0)
    by 0x498F42A: wfl_checked_display_connect (piglit-util-waffle.h:74)

There is one more thing which disallow us to easily fix it are different element sizes
for instance: `glx_config_create_list` allocates memory just for `glx_config`,
`driwindowsMapConfigs` for `driwindows_config` and
`createDriMode` for `__GLXDRIconfigPrivate`.
Yes it is possible but size of such fix
will be more big and complex than original one.
So it make sense only if the malloc overhead
really is a big problem there.

Acked-by: Eric Engestrom <eric@engestrom.ch>
Signed-off-by: Andrii Simiklit <andrii.simiklit@globallogic.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3406>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3406>
(cherry picked from commit 311c82e1923f63070b198881d90c1098f4ff7a08)

2 files changed, 38 insertions, 27 deletions

diff --git a/.pick_status.json b/.pick_status.json
index 241ed9ff4f2..1a945a92853 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -1363,7 +1363,7 @@
         "description": "Revert \"glx: convert glx_config_create_list to one big calloc\"",
         "nominated": true,
         "nomination_type": 2,
-        "resolution": 0,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": "35fc7bdf0e6ad6547e39099e7060a3d89539b56d"
     },
diff --git a/src/glx/glxconfig.c b/src/glx/glxconfig.c
index 569d24bfac5..6c4267c8f39 100644
--- a/src/glx/glxconfig.c
+++ b/src/glx/glxconfig.c
@@ -218,43 +218,54 @@ glx_config_get(struct glx_config * mode, int attribute, int *value_return)
 _X_HIDDEN struct glx_config *
 glx_config_create_list(unsigned count)
 {
-   struct glx_config *c = NULL;
+   const size_t size = sizeof(struct glx_config);
+   struct glx_config *base = NULL;
+   struct glx_config **next;
    unsigned i;
 
-   if (!(c = calloc(count, sizeof(struct glx_config))))
-      return NULL;
-
+   next = &base;
    for (i = 0; i < count; i++) {
-      c[i].visualID = GLX_DONT_CARE;
-      c[i].visualType = GLX_DONT_CARE;
-      c[i].visualRating = GLX_NONE;
-      c[i].transparentPixel = GLX_NONE;
-      c[i].transparentRed = GLX_DONT_CARE;
-      c[i].transparentGreen = GLX_DONT_CARE;
-      c[i].transparentBlue = GLX_DONT_CARE;
-      c[i].transparentAlpha = GLX_DONT_CARE;
-      c[i].transparentIndex = GLX_DONT_CARE;
-      c[i].xRenderable = GLX_DONT_CARE;
-      c[i].fbconfigID = GLX_DONT_CARE;
-      c[i].swapMethod = GLX_SWAP_UNDEFINED_OML;
-      c[i].bindToTextureRgb = GLX_DONT_CARE;
-      c[i].bindToTextureRgba = GLX_DONT_CARE;
-      c[i].bindToMipmapTexture = GLX_DONT_CARE;
-      c[i].bindToTextureTargets = GLX_DONT_CARE;
-      c[i].yInverted = GLX_DONT_CARE;
-      c[i].sRGBCapable = GLX_DONT_CARE;
+      *next = calloc(1, size);
+      if (*next == NULL) {
+	 glx_config_destroy_list(base);
+	 base = NULL;
+	 break;
+      }
+
+      (*next)->visualID = GLX_DONT_CARE;
+      (*next)->visualType = GLX_DONT_CARE;
+      (*next)->visualRating = GLX_NONE;
+      (*next)->transparentPixel = GLX_NONE;
+      (*next)->transparentRed = GLX_DONT_CARE;
+      (*next)->transparentGreen = GLX_DONT_CARE;
+      (*next)->transparentBlue = GLX_DONT_CARE;
+      (*next)->transparentAlpha = GLX_DONT_CARE;
+      (*next)->transparentIndex = GLX_DONT_CARE;
+      (*next)->xRenderable = GLX_DONT_CARE;
+      (*next)->fbconfigID = GLX_DONT_CARE;
+      (*next)->swapMethod = GLX_SWAP_UNDEFINED_OML;
+      (*next)->bindToTextureRgb = GLX_DONT_CARE;
+      (*next)->bindToTextureRgba = GLX_DONT_CARE;
+      (*next)->bindToMipmapTexture = GLX_DONT_CARE;
+      (*next)->bindToTextureTargets = GLX_DONT_CARE;
+      (*next)->yInverted = GLX_DONT_CARE;
+      (*next)->sRGBCapable = GLX_DONT_CARE;
 
-      if (i != count -1)
-         c[i].next = &(c[i+1]);
+      next = &((*next)->next);
    }
 
-   return c;
+   return base;
 }
 
 _X_HIDDEN void
 glx_config_destroy_list(struct glx_config *configs)
 {
-   free(configs);
+   while (configs != NULL) {
+      struct glx_config *const next = configs->next;
+
+      free(configs);
+      configs = next;
+   }
 }