From 2edf5a958484f8dc8fb6d3be14606852b696e379 Mon Sep 17 00:00:00 2001
From: Ray <raysan5@gmail.com>
Date: Tue, 29 Nov 2022 10:45:10 +0100
Subject: [PATCH] REVIEWED: Issue with shader linkage

---
 src/rcore.c | 11 +++++++----
 src/rlgl.h  |  6 ++++--
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/rcore.c b/src/rcore.c
index 8f5b63b15..118a5736b 100644
--- a/src/rcore.c
+++ b/src/rcore.c
@@ -2446,10 +2446,6 @@ Shader LoadShader(const char *vsFileName, const char *fsFileName)
 Shader LoadShaderFromMemory(const char *vsCode, const char *fsCode)
 {
     Shader shader = { 0 };
-    shader.locs = (int *)RL_CALLOC(RL_MAX_SHADER_LOCATIONS, sizeof(int));
-
-    // NOTE: All locations must be reseted to -1 (no location)
-    for (int i = 0; i < RL_MAX_SHADER_LOCATIONS; i++) shader.locs[i] = -1;
 
     shader.id = rlLoadShaderCode(vsCode, fsCode);
 
@@ -2465,6 +2461,11 @@ Shader LoadShaderFromMemory(const char *vsCode, const char *fsCode)
         //          vertex texcoord2 location   = 5
 
         // NOTE: If any location is not found, loc point becomes -1
+        
+        shader.locs = (int *)RL_CALLOC(RL_MAX_SHADER_LOCATIONS, sizeof(int));
+
+        // All locations reseted to -1 (no location)
+        for (int i = 0; i < RL_MAX_SHADER_LOCATIONS; i++) shader.locs[i] = -1;
 
         // Get handles to GLSL input attibute locations
         shader.locs[SHADER_LOC_VERTEX_POSITION] = rlGetLocationAttrib(shader.id, RL_DEFAULT_SHADER_ATTRIB_NAME_POSITION);
@@ -2497,6 +2498,8 @@ void UnloadShader(Shader shader)
     if (shader.id != rlGetShaderIdDefault())
     {
         rlUnloadShaderProgram(shader.id);
+        
+        // NOTE: If shader loading failed, it should be 0
         RL_FREE(shader.locs);
     }
 }
diff --git a/src/rlgl.h b/src/rlgl.h
index 04fcf8f91..e4f65d69a 100644
--- a/src/rlgl.h
+++ b/src/rlgl.h
@@ -3643,12 +3643,14 @@ unsigned int rlLoadShaderCode(const char *vsCode, const char *fsCode)
         // NOTE: We detach shader before deletion to make sure memory is freed
         if (vertexShaderId != RLGL.State.defaultVShaderId)
         {
-            glDetachShader(id, vertexShaderId);
+            // WARNING: Shader program linkage could fail and returned id is 0
+            if (id > 0) glDetachShader(id, vertexShaderId);
             glDeleteShader(vertexShaderId);
         }
         if (fragmentShaderId != RLGL.State.defaultFShaderId)
         {
-            glDetachShader(id, fragmentShaderId);
+            // WARNING: Shader program linkage could fail and returned id is 0
+            if (id > 0) glDetachShader(id, fragmentShaderId);
             glDeleteShader(fragmentShaderId);
         }