add NORETURN_PTR for function pointers

Some compilers (including at least MSVC and ARM RVDS) supports
NORETURN on function declarations, but not on function pointers.

This patch makes it possible to define NORETURN for these compilers,
by splitting the NORETURN macro into two - one for function
declarations and one for function pointers.
Signed-off-by: NErik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: NJeff King <peff@peff.net>

git-compat-util.h

@@ -176,8 +176,10 @@ extern char *gitbasename(char *);
 
 #ifdef __GNUC__
 #define NORETURN __attribute__((__noreturn__))
+#define NORETURN_PTR __attribute__((__noreturn__))
 #else
 #define NORETURN
+#define NORETURN_PTR
 #ifndef __attribute__
 #define __attribute__(x)
 #endif
@@ -192,7 +194,7 @@ extern NORETURN void die_errno(const char *err, ...) __attribute__((format (prin
 extern int error(const char *err, ...) __attribute__((format (printf, 1, 2)));
 extern void warning(const char *err, ...) __attribute__((format (printf, 1, 2)));
 
-extern void set_die_routine(NORETURN void (*routine)(const char *err, va_list params));
+extern void set_die_routine(NORETURN_PTR void (*routine)(const char *err, va_list params));
 
 extern int prefixcmp(const char *str, const char *prefix);
 extern time_t tm_to_time_t(const struct tm *tm);

usage.c

@@ -36,12 +36,12 @@ static void warn_builtin(const char *warn, va_list params)
 
 /* If we are in a dlopen()ed .so write to a global variable would segfault
  * (ugh), so keep things static. */
-static NORETURN void (*usage_routine)(const char *err) = usage_builtin;
-static NORETURN void (*die_routine)(const char *err, va_list params) = die_builtin;
+static NORETURN_PTR void (*usage_routine)(const char *err) = usage_builtin;
+static NORETURN_PTR void (*die_routine)(const char *err, va_list params) = die_builtin;
 static void (*error_routine)(const char *err, va_list params) = error_builtin;
 static void (*warn_routine)(const char *err, va_list params) = warn_builtin;
 
-void set_die_routine(NORETURN void (*routine)(const char *err, va_list params))
+void set_die_routine(NORETURN_PTR void (*routine)(const char *err, va_list params))
 {
 	die_routine = routine;
 }