From: Junio C Hamano Date: Tue, 08 Jan 2008 20:13:13 GMT Subject: Re: [PATCH 1/2] sideband.c: Use xmalloc() instead of variable-sized arrays. Message-ID: <7v7iikrs86.fsf@gitster.siamese.dyndns.org> In-Reply-To: Nicolas Pitre writes: > On Tue, 8 Jan 2008, Junio C Hamano wrote: > >> Johannes Sixt writes: >> >> > From: Johannes Sixt >> > >> > How come we got along with this not very portable construct for so long? >> > Probably because the array sizes were computed from the results of >> > strlen() of string constants. Anyway, a follow-up patch will make the >> > lengths really non-constant. >> > >> > Signed-off-by: Johannes Sixt >> > --- >> > sideband.c | 14 ++++++++++++-- >> > 1 files changed, 12 insertions(+), 2 deletions(-) >> > >> > diff --git a/sideband.c b/sideband.c >> > index 756bbc2..513d7b3 100644 >> > --- a/sideband.c >> > +++ b/sideband.c >> > @@ -19,7 +19,10 @@ int recv_sideband(const char *me, int in_stream, int out, int err) >> > { >> > unsigned pf = strlen(PREFIX); >> > unsigned sf = strlen(SUFFIX); >> > - char buf[pf + LARGE_PACKET_MAX + sf + 1]; >> > + char *buf, *save; >> > + >> > + save = xmalloc(sf); >> > + buf = xmalloc(pf + LARGE_PACKET_MAX + sf + 1); >> >> I have to wonder if the malloc() overhead is small enough >> compared to the network bandwidth to make a two malloc-free >> pairs per packet a non-issue... > > Eeek. Overhead might be insignificant, but it still doesn't feel right. > > What about using alloca() instead? This is not like if we are doing > funky things with the allocated memory anyway. That's double Eek as I recall AIX is not dead. How about using a constant large enough slop? It is not like PREFIX and SUFFIX are different vastly between calls.