From dfa17bf9673082e658d50369c2a292380cc08a5d Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <icculus@icculus.org>
Date: Fri, 4 May 2018 17:45:20 -0400
Subject: [PATCH] Always return a non-NULL pointer for malloc(0).

Some C runtimes, like musl, will return NULL in this case. It's more
convenient to not get a NULL (which is meant to be interpreted as a failure),
but instead get a non-NULL pointer that can't be dereferenced (because
it's a pointer to zero bytes of memory).
---
 mojoshader.c              | 6 ++++--
 mojoshader_assembler.c    | 6 ++++--
 mojoshader_compiler.c     | 6 ++++--
 mojoshader_opengl.c       | 5 +++--
 mojoshader_preprocessor.c | 6 ++++--
 5 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/mojoshader.c b/mojoshader.c
index 255d68a6..36294923 100644
--- a/mojoshader.c
+++ b/mojoshader.c
@@ -307,9 +307,10 @@ static inline void out_of_memory(Context *ctx)
     ctx->isfail = ctx->out_of_memory = 1;
 } // out_of_memory
 
+static char zeromalloc = 0;
 static inline void *Malloc(Context *ctx, const size_t len)
 {
-    void *retval = ctx->malloc((int) len, ctx->malloc_data);
+    void *retval = (len == 0) ? &zeromalloc : ctx->malloc((int) len, ctx->malloc_data);
     if (retval == NULL)
         out_of_memory(ctx);
     return retval;
@@ -325,7 +326,8 @@ static inline char *StrDup(Context *ctx, const char *str)
 
 static inline void Free(Context *ctx, void *ptr)
 {
-    ctx->free(ptr, ctx->malloc_data);
+    if ((ptr != &zeromalloc) && (ptr != NULL))
+        ctx->free(ptr, ctx->malloc_data);
 } // Free
 
 static void * MOJOSHADERCALL MallocBridge(int bytes, void *data)
diff --git a/mojoshader_assembler.c b/mojoshader_assembler.c
index c9148410..0621af85 100644
--- a/mojoshader_assembler.c
+++ b/mojoshader_assembler.c
@@ -72,9 +72,10 @@ static inline void out_of_memory(Context *ctx)
     ctx->isfail = ctx->out_of_memory = 1;
 } // out_of_memory
 
+static char zeromalloc = 0;
 static inline void *Malloc(Context *ctx, const size_t len)
 {
-    void *retval = ctx->malloc((int) len, ctx->malloc_data);
+    void *retval = (len == 0) ? &zeromalloc : ctx->malloc((int) len, ctx->malloc_data);
     if (retval == NULL)
         out_of_memory(ctx);
     return retval;
@@ -90,7 +91,8 @@ static inline char *StrDup(Context *ctx, const char *str)
 
 static inline void Free(Context *ctx, void *ptr)
 {
-    ctx->free(ptr, ctx->malloc_data);
+    if ((ptr != &zeromalloc) && (ptr != NULL))
+        ctx->free(ptr, ctx->malloc_data);
 } // Free
 
 static void *MallocBridge(int bytes, void *data)
diff --git a/mojoshader_compiler.c b/mojoshader_compiler.c
index 3e49ff64..012997cb 100644
--- a/mojoshader_compiler.c
+++ b/mojoshader_compiler.c
@@ -160,9 +160,10 @@ static inline void out_of_memory(Context *ctx)
     ctx->isfail = ctx->out_of_memory = 1;
 } // out_of_memory
 
+static char zeromalloc = 0;
 static inline void *Malloc(Context *ctx, const size_t len)
 {
-    void *retval = ctx->malloc((int) len, ctx->malloc_data);
+    void *retval = (len == 0) ? &zeromalloc : ctx->malloc((int) len, ctx->malloc_data);
     if (retval == NULL)
         out_of_memory(ctx);
     return retval;
@@ -178,7 +179,8 @@ static inline char *StrDup(Context *ctx, const char *str)
 
 static inline void Free(Context *ctx, void *ptr)
 {
-    ctx->free(ptr, ctx->malloc_data);
+    if ((ptr != &zeromalloc) && (ptr != NULL))
+        ctx->free(ptr, ctx->malloc_data);
 } // Free
 
 static void *MallocBridge(int bytes, void *data)
diff --git a/mojoshader_opengl.c b/mojoshader_opengl.c
index 08b9773f..2e88e358 100644
--- a/mojoshader_opengl.c
+++ b/mojoshader_opengl.c
@@ -347,9 +347,10 @@ static inline void out_of_memory(void)
     set_error("out of memory");
 } // out_of_memory
 
+static char zeromalloc = 0;
 static inline void *Malloc(const size_t len)
 {
-    void *retval = ctx->malloc_fn((int) len, ctx->malloc_data);
+    void *retval = (len == 0) ? &zeromalloc : ctx->malloc_fn((int) len, ctx->malloc_data);
     if (retval == NULL)
         out_of_memory();
     return retval;
@@ -357,7 +358,7 @@ static inline void *Malloc(const size_t len)
 
 static inline void Free(void *ptr)
 {
-    if (ptr != NULL)
+    if ((ptr != &zeromalloc) && (ptr != NULL))
         ctx->free_fn(ptr, ctx->malloc_data);
 } // Free
 
diff --git a/mojoshader_preprocessor.c b/mojoshader_preprocessor.c
index 5b5090ba..664b530e 100644
--- a/mojoshader_preprocessor.c
+++ b/mojoshader_preprocessor.c
@@ -68,9 +68,10 @@ static inline void out_of_memory(Context *ctx)
     ctx->out_of_memory = 1;
 } // out_of_memory
 
+static char zeromalloc = 0;
 static inline void *Malloc(Context *ctx, const size_t len)
 {
-    void *retval = ctx->malloc((int) len, ctx->malloc_data);
+    void *retval = (len == 0) ? &zeromalloc : ctx->malloc((int) len, ctx->malloc_data);
     if (retval == NULL)
         out_of_memory(ctx);
     return retval;
@@ -78,7 +79,8 @@ static inline void *Malloc(Context *ctx, const size_t len)
 
 static inline void Free(Context *ctx, void *ptr)
 {
-    ctx->free(ptr, ctx->malloc_data);
+    if ((ptr != &zeromalloc) && (ptr != NULL))
+        ctx->free(ptr, ctx->malloc_data);
 } // Free
 
 static void *MallocBridge(int bytes, void *data)