Re: Re: Homebrew and Git

[Jeff King <peff@peff.net>]

On Tue, Sep 20, 2016 at 08:15:55PM +0100, John Keeping wrote:

> > BTW, here is the callstack inlined from the crashreport:
> > 
> > bsystem_platform.dylib      	0x00007fff840db41c _platform_strchr$VARIANT$Haswell + 28
> > 1   git                           	0x000000010ba1d3f4 ident_default_email + 801
> > 2   git                           	0x000000010ba1d68f fmt_ident + 66
> > 3   git                           	0x000000010ba4b495 files_log_ref_write + 175
> > 4   git                           	0x000000010ba4b0a6 commit_ref_update + 106
> > 5   git                           	0x000000010ba4c3a8 ref_transaction_commit + 468
> > 6   git                           	0x000000010b994dd8 s_update_ref + 271
> > 7   git                           	0x000000010b994556 fetch_refs + 1969
> > 8   git                           	0x000000010b9935f2 fetch_one + 1913
> > 9   git                           	0x000000010b992bc4 cmd_fetch + 549
> > 10  git                           	0x000000010b9666c4 handle_builtin + 478
> > 11  git                           	0x000000010b96602f main + 376
> > 12  libdyld.dylib                 	0x00007fff834ef5ad start + 1
> > 
> > Maybe someone else has an idea what might be causing this...
> 
> The only strchr I can see that could be called here is in
> canonical_name(), where it's called with addrinfo::ai_canonname.

There's one in add_domainname(), too, but it can never be NULL (we could
walk off the end of the buffer, but only if gethostname() lies to us
about its result code, which seems unlikely). So I agree it's probably
the call in canonical_name().

> Searching for OS X and ai_canonname, leads me straight back to this
> list, although 7 years ago!  I think ident.c needs a fix similar to
> commit 3e8a00a (daemon.c: fix segfault on OS X, 2009-04-27); from the
> commit message there:
> 
> 	On OS X (and maybe other unices), getaddrinfo(3) returns NULL
> 	in the ai_canonname field if it's called with an IP address for
> 	the hostname.

Interesting. We are already prepared for failure from getaddrinfo()
here, so probably:

diff --git a/ident.c b/ident.c
index e20a772..d17b5bd 100644
--- a/ident.c
+++ b/ident.c
@@ -101,7 +101,7 @@ static int canonical_name(const char *host, struct strbuf *out)
 	memset (&hints, '\0', sizeof (hints));
 	hints.ai_flags = AI_CANONNAME;
 	if (!getaddrinfo(host, NULL, &hints, &ai)) {
-		if (ai && strchr(ai->ai_canonname, '.')) {
+		if (ai && ai->ai_canonname && strchr(ai->ai_canonname, '.')) {
 			strbuf_addstr(out, ai->ai_canonname);
 			status = 0;
 		}

would be sufficient. Jonas, can you see if that patch helps?

-Peff