Re: git master describe segfault

Daniel Stenberg [off-list ref] writes:

0. I'm on a Linux box: a reasonably updated Debian unstable.

1. I'm up to date with the latest git master branch of gecko-dev:
https://github.com/mozilla/gecko-dev (counting a little over 467K
commits)

2. I built the current git off the master branch (v2.8.0-rc3-12-g047057b)

3. In the gecko-dev dir, I run 'git describe --contains f495d0cc2'

The outcome is what looks like a fine stack smash due to very very
extensive recursion:

$ gdb --args ../git/git describe --contains f495d0cc2
(gdb) run
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7bccf73 in ?? () from /lib/x86_64-linux-gnu/libz.so.1
...
#12 0x0000000000464662 in name_rev (commit=0x170df20,
tip_name=0x8e9170 "B2G_1_0_0_20130115070201", generation=87254,
distance=87254, deref=0) at builtin/name-rev.c:30
#13 0x00000000004647de in name_rev (commit=0x170dee0,
tip_name=0x8e9170 "B2G_1_0_0_20130115070201", generation=87253,
distance=87253, deref=0) at builtin/name-rev.c:72
#14 0x00000000004647de in name_rev (commit=0x170dea0,
tip_name=0x8e9170 "B2G_1_0_0_20130115070201", generation=87252,
distance=87252, deref=0) at builtin/name-rev.c:72
#15 0x00000000004647de in name_rev (commit=0x170de60,
tip_name=0x8e9170 "B2G_1_0_0_20130115070201", generation=87251,
distance=87251, deref=0) at builtin/name-rev.c:72
#16 0x00000000004647de in name_rev (commit=0x170de20,
tip_name=0x8e9170 "B2G_1_0_0_20130115070201", generation=87250,
distance=87250, deref=0) at builtin/name-rev.c:72
#17 0x00000000004647de in name_rev (commit=0x170dde0,
tip_name=0x8e9170 "B2G_1_0_0_20130115070201", generation=87249,
distance=87249, deref=0) at builtin/name-rev.c:72

It does look bad.  name_rev() naively recurses quite a lot and
easily runs out of stack space, it seems (rewriting the recursion
to iterative implementation may help).  I haven't looked at this
code carefully for quite a while, but I suspect piece of memory
pointed at by new_name variable may also be leaking.