Customizable error handlers

This patch makes the usage(), die() and error() handlers customizable.
Nothing in the git code itself uses that but many other libgit users
(like Git.pm) will.

This is implemented using the mutator functions primarily because you
cannot directly modifying global variables of libgit from a program that
dlopen()ed it, apparently. But having functions for that is a better API
anyway.

Signed-off-by: Petr Baudis <pasky@suse.cz>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 42 insertions, 4 deletions

diff --git a/usage.c b/usage.c
index 1fa924c3d9..b781b0061e 100644
--- a/usage.c
+++ b/usage.c
@@ -12,20 +12,58 @@ static void report(const char *prefix, const char *err, va_list params)
 	fputs("\n", stderr);
 }
 
-void usage(const char *err)
+void usage_builtin(const char *err)
 {
 	fprintf(stderr, "usage: %s\n", err);
 	exit(129);
 }
 
+void die_builtin(const char *err, va_list params)
+{
+	report("fatal: ", err, params);
+	exit(128);
+}
+
+void error_builtin(const char *err, va_list params)
+{
+	report("error: ", err, params);
+}
+
+
+/* If we are in a dlopen()ed .so write to a global variable would segfault
+ * (ugh), so keep things static. */
+static void (*usage_routine)(const char *err) NORETURN = usage_builtin;
+static void (*die_routine)(const char *err, va_list params) NORETURN = die_builtin;
+static void (*error_routine)(const char *err, va_list params) = error_builtin;
+
+void set_usage_routine(void (*routine)(const char *err) NORETURN)
+{
+	usage_routine = routine;
+}
+
+void set_die_routine(void (*routine)(const char *err, va_list params) NORETURN)
+{
+	die_routine = routine;
+}
+
+void set_error_routine(void (*routine)(const char *err, va_list params))
+{
+	error_routine = routine;
+}
+
+
+void usage(const char *err)
+{
+	usage_routine(err);
+}
+
 void die(const char *err, ...)
 {
 	va_list params;
 
 	va_start(params, err);
-	report("fatal: ", err, params);
+	die_routine(err, params);
 	va_end(params);
-	exit(128);
 }
 
 int error(const char *err, ...)
@@ -33,7 +71,7 @@ int error(const char *err, ...)
 	va_list params;
 
 	va_start(params, err);
-	report("error: ", err, params);
+	error_routine(err, params);
 	va_end(params);
 	return -1;
 }