mapi: add new _glapi_new_nop_table() and _glapi_set_nop_handler()

_glapi_new_nop_table() creates a new dispatch table populated with
pointers to no-op functions.

_glapi_set_nop_handler() is used to register a callback function which
will be called from each of the no-op functions.

Now we always generate a separate no-op function for each GL entrypoint.
This allows us to do proper stack clean-up for Windows __stdcall and
lets us report the actual function name in error messages.  Before this
change, for non-Windows release builds we used a single no-op function
for all entrypoints.

Reviewed-by: Jose Fonseca <[email protected]>

2 files changed, 59 insertions, 36 deletions

diff --git a/src/mapi/glapi/glapi.h b/src/mapi/glapi/glapi.h
index 8d991fb3b8a..673295bca46 100644
--- a/src/mapi/glapi/glapi.h
+++ b/src/mapi/glapi/glapi.h
@@ -80,6 +80,9 @@ extern "C" {
 #endif
 
 typedef void (*_glapi_proc)(void);
+
+typedef void (*_glapi_nop_handler_proc)(const char *name);
+
 struct _glapi_table;
 
 
@@ -159,6 +162,14 @@ _GLAPI_EXPORT struct _glapi_table *
 _glapi_create_table_from_handle(void *handle, const char *symbol_prefix);
 
 
+_GLAPI_EXPORT void
+_glapi_set_nop_handler(_glapi_nop_handler_proc func);
+
+/** Return pointer to new dispatch table filled with no-op functions */
+_GLAPI_EXPORT struct _glapi_table *
+_glapi_new_nop_table(unsigned num_entries);
+
+
 /** Deprecated function */
 _GLAPI_EXPORT unsigned long
 _glthread_GetID(void);
diff --git a/src/mapi/glapi/glapi_nop.c b/src/mapi/glapi/glapi_nop.c
index 628276e932b..0041ed5a876 100644
--- a/src/mapi/glapi/glapi_nop.c
+++ b/src/mapi/glapi/glapi_nop.c
@@ -30,14 +30,21 @@
  * This file defines a special dispatch table which is loaded with no-op
  * functions.
  *
- * When there's no current rendering context, calling a GL function like
- * glBegin() is a no-op.  Apps should never normally do this.  So as a
- * debugging aid, each of the no-op functions will emit a warning to
- * stderr if the MESA_DEBUG or LIBGL_DEBUG env var is set.
+ * Mesa can register a "no-op handler function" which will be called in
+ * the event that a no-op function is called.
+ *
+ * In the past, the dispatch table was loaded with pointers to a single
+ * no-op function.  But that broke on Windows because the GL entrypoints
+ * use __stdcall convention.  __stdcall means the callee cleans up the
+ * stack.  So one no-op function can't properly clean up the stack.  This
+ * would lead to crashes.
+ *
+ * Another benefit of unique no-op functions is we can accurately report
+ * the function's name in an error message.
  */
 
 
-
+#include <string.h>
 #include "glapi/glapi_priv.h"
 
 
@@ -51,25 +58,32 @@ _glapi_set_warning_func(_glapi_proc func)
 {
 }
 
-/*
- * When GLAPIENTRY is __stdcall (i.e. Windows), the stack is popped by the
- * callee making the number/type of arguments significant.
+
+/**
+ * We'll jump though this function pointer whenever a no-op function
+ * is called.
  */
-#if defined(_WIN32) || defined(DEBUG)
+static _glapi_nop_handler_proc nop_handler = NULL;
+
+
+/**
+ * Register the no-op handler call-back function.
+ */
+void
+_glapi_set_nop_handler(_glapi_nop_handler_proc func)
+{
+   nop_handler = func;
+}
+
 
 /**
  * Called by each of the no-op GL entrypoints.
  */
-static int
-Warn(const char *func)
+static void
+nop(const char *func)
 {
-#if defined(DEBUG)
-   if (getenv("MESA_DEBUG") || getenv("LIBGL_DEBUG")) {
-      fprintf(stderr, "GL User Error: gl%s called without a rendering context\n",
-              func);
-   }
-#endif
-   return 0;
+   if (nop_handler)
+      nop_handler(func);
 }
 
 
@@ -79,7 +93,8 @@ Warn(const char *func)
 static GLint
 NoOpUnused(void)
 {
-   return Warn(" function");
+   nop("unused GL entry point");
+   return 0;
 }
 
 /*
@@ -89,31 +104,28 @@ NoOpUnused(void)
 #define KEYWORD1_ALT static
 #define KEYWORD2 GLAPIENTRY
 #define NAME(func)  NoOp##func
-#define DISPATCH(func, args, msg)  Warn(#func);
-#define RETURN_DISPATCH(func, args, msg)  Warn(#func); return 0
+#define DISPATCH(func, args, msg)  nop(#func);
+#define RETURN_DISPATCH(func, args, msg)  nop(#func); return 0
 
 
 /*
  * Defines for the table of no-op entry points.
  */
 #define TABLE_ENTRY(name) (_glapi_proc) NoOp##name
+#define DISPATCH_TABLE_NAME __glapi_noop_table
+#define UNUSED_TABLE_NAME __unused_noop_functions
+
+#include "glapi/glapitemp.h"
 
-#else
 
-static int
-NoOpGeneric(void)
+/** Return pointer to new dispatch table filled with no-op functions */
+struct _glapi_table *
+_glapi_new_nop_table(unsigned num_entries)
 {
-   if (getenv("MESA_DEBUG") || getenv("LIBGL_DEBUG")) {
-      fprintf(stderr, "GL User Error: calling GL function without a rendering context\n");
+   struct _glapi_table *table = malloc(num_entries * sizeof(_glapi_proc));
+   if (table) {
+      memcpy(table, __glapi_noop_table,
+             num_entries * sizeof(_glapi_proc));
    }
-   return 0;
+   return table;
 }
-
-#define TABLE_ENTRY(name) (_glapi_proc) NoOpGeneric
-
-#endif
-
-#define DISPATCH_TABLE_NAME __glapi_noop_table
-#define UNUSED_TABLE_NAME __unused_noop_functions
-
-#include "glapi/glapitemp.h"