Subject: [PATCH] Add a knob to abort on die() (was Re: git checkout crashes after ...)

From: Duy Nguyen <[email-masked]>
Date: Wed, 19 Oct 2016 20:47:50 +0700

On Wed, Oct 19, 2016 at 08:27:43PM +0700, Duy Nguyen wrote:
> If you set the environment variable GIT_ALLOC_LIMIT ...  git
> attempts to allocate more than that ... then it's caught and we get
> a glimpse of how much memory git may need. Unfortunately we can't
> get a stack trace or anything like that unless you rebuild Git from
> source.

It's moments like this that I wish we had a knob to force core
dumps. And I often modify die_builtin() to add '*(char*)0 = 1;' to
force a core dump when I can't figure out some problem based on the
error message alone.

So.. how about we do something like this? We could extend it to abort
on error() as well as die(). Aborting on warning() may be a bit too
much though. On glibc systems we could even print the back trace
without aborting, which helps in some cases.

The long variable name and value are on purpose to hopefully not
trigger this by mistake.

diff --git a/git.c b/git.c
index ab5c99c..5fea224 100644
--- a/git.c
+++ b/git.c
@@ -622,15 +622,34 @@ static int run_argv(int *argcp, const char ***argv)
 	return done_alias;
 }
 
+static NORETURN void die_by_aborting(const char *err, va_list params)
+{
+	vreportf("fatal: ", err, params);
+	abort();
+}
+
+static NORETURN void die_silently_by_aborting(const char *err, va_list params)
+{
+	abort();
+}
+
 int cmd_main(int argc, const char **argv)
 {
 	const char *cmd;
 	int done_help = 0;
+	const char *die_abort_env = getenv("GIT_ABORT_ON_FATAL_ERRORS");
 
 	cmd = argv[0];
 	if (!cmd)
 		cmd = "git-help";
 
+	if (die_abort_env) {
+		if (!strcmp(die_abort_env, "yes please"))
+			set_die_routine(die_by_aborting);
+		else if (!strcmp(die_abort_env, "just die"))
+			set_die_routine(die_silently_by_aborting);
+	}
+
 	trace_command_performance(argv);
 
 	/*
--
Duy