[PATCH] Makefile: add a note about the NO_MMAP setting on IRIX and IRIX64

Brandon Casey· Oct 9, 2009, 00:09 UTC · lore

From: Brandon Casey <drafnel@gmail.com>

When git is compiled with the MIPSpro 7.4.4m compiler, and NO_PTHREADS is set, and NO_MMAP is _not_ set, then git segfaults when trying to access the first entry in a reflog. If NO_PTHREADS is not set (which implies that the pthread library is linked in), or NO_MMAP _is_ set, then the segfault is not encountered. The conservative choise has been made to set NO_MMAP in the Makefile to avoid this flaw. The GNU C compiler does not produce this behavior.

The segfault happens in refs.c:read_ref_at(). The mmap succeeds, and the loop is executed properly until rec is rewound into the first line (reflog entry) of the file. The segfault is caught by test 28 of t1400-update-ref.sh which fails when 'git rev-parse --verify "master@{May 25 2005}"' is called.

So, add a comment in the Makefile to describe why NO_MMAP is set and as a hint to those who may be interested in unsetting it.

Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
---
 Makefile |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

Show changes to Makefile +12 −0

diff --git a/Makefile b/Makefile
index dd3d520..a340fb1 100644
--- a/Makefile
+++ b/Makefile
@@ -841,6 +841,12 @@ ifeq ($(uname_S),IRIX)
 	NO_MEMMEM = YesPlease
 	NO_MKSTEMPS = YesPlease
 	NO_MKDTEMP = YesPlease
+	# When compiled with the MIPSpro 7.4.4m compiler, and without pthreads
+	# (i.e. NO_PTHREADS is set), and _with_ MMAP (i.e. NO_MMAP is not set),
+	# git dies with a segmentation fault when trying to access the first
+	# entry of a reflog.  The conservative choice is made to always set
+	# NO_MMAP.  If you suspect that your compiler is not affected by this
+	# issue, comment out the NO_MMAP statement.
 	NO_MMAP = YesPlease
 	NO_EXTERNAL_GREP = UnfortunatelyYes
 	SNPRINTF_RETURNS_BOGUS = YesPlease
@@ -854,6 +860,12 @@ ifeq ($(uname_S),IRIX64)
 	NO_MEMMEM = YesPlease
 	NO_MKSTEMPS = YesPlease
 	NO_MKDTEMP = YesPlease
+	# When compiled with the MIPSpro 7.4.4m compiler, and without pthreads
+	# (i.e. NO_PTHREADS is set), and _with_ MMAP (i.e. NO_MMAP is not set),
+	# git dies with a segmentation fault when trying to access the first
+	# entry of a reflog.  The conservative choice is made to always set
+	# NO_MMAP.  If you suspect that your compiler is not affected by this
+	# issue, comment out the NO_MMAP statement.
 	NO_MMAP = YesPlease
 	NO_EXTERNAL_GREP = UnfortunatelyYes
 	SNPRINTF_RETURNS_BOGUS = YesPlease

-- 
1.6.5.rc2.17.gdbc1b

Brandon Casey· Oct 9, 2009, 00:15 UTC · re: Brandon Casey · lore

Re: [PATCH] Makefile: add a note about the NO_MMAP setting on IRIX and IRIX64

Brandon Casey wrote:

Show 7 quoted lines

> From: Brandon Casey <drafnel@gmail.com>
> 
> When git is compiled with the MIPSpro 7.4.4m compiler, and NO_PTHREADS is
> set, and NO_MMAP is _not_ set, then git segfaults when trying to access the
> first entry in a reflog.  If NO_PTHREADS is not set (which implies that the
> pthread library is linked in), or NO_MMAP _is_ set, then the segfault is
> not encountered.  The conservative choise has been made to set NO_MMAP in

^^^

I misspelled 'choice'. Doesn't seem worth a resend. If you can fix it before you apply, that would be great. If you forget, no big deal.

-brandon

patchMakefile: add a note about the NO_MMAP setting on IRIX and IRIX64