Re: [RFC/PATCH] userdiff.c: Avoid old glibc regex bug causing t4034-*.sh test failures

[Ramsay Jones <ramsay@ramsay1.demon.co.uk>]

Jonathan Nieder wrote:
> Ramsay Jones wrote:
>> This is an RFC because:
>>     - A simple fix would be for me to put NO_REGEX=1 in my config.mak,
>>       since the compat/regex routines don't suffer this problem.
>>     - I suspect this bug is old enough that it will not affect many users.
>>     - I have not audited the other non-matching list expressions in
>>       userdiff.c
>>     - blame, grep and pickaxe all call regcomp() with the REG_NEWLINE
>>       flag, but get the regex from the user (eg from command line).
> 
> I think excluding \n along with ' ' and \t in similar places makes
> sense, ...

I briefly considered replacing ' \t' with [:space:], but that would
also add \v, \f and \r in addition to \n (and, maybe, some locale
specific chars too), so I decided not to go that route ...

>        ... but that meanwhile we should add tests to the testsuite for
> blame/grep/pickaxe to catch such implementations failing when
> NO_REGEX=1 is not set.

Hmm, well I would certainly never complain about additional tests, but
who would these tests benefit? I suspect that the number of people
building git from source on an old (pre about 2008 say) glibc system
with this bug is somewhat small. (Of course I have no numbers to back
up that gut feeling! :-))

Having said that, I have attached a patch (below), that adds a test
(to t0070-fundamental.sh) using a stand-alone test-regex program, in
order to simplify the detection of this bug.

What do you think? (would this exchange in the list-archive suffice?)

> Does that make sense?  Thanks for tracking this down.

No problem.

ATB,
Ramsay Jones

-- >8 --
Subject: [PATCH] test-regex: Add a test to check for a bug in the regex routines


Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
---
 .gitignore             |    1 +
 Makefile               |    1 +
 t/t0070-fundamental.sh |    5 +++++
 test-regex.c           |   35 +++++++++++++++++++++++++++++++++++
 4 files changed, 42 insertions(+), 0 deletions(-)
 create mode 100644 test-regex.c

diff --git a/.gitignore b/.gitignore
index 711fce7..70af8b1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -174,6 +174,7 @@
 /test-obj-pool
 /test-parse-options
 /test-path-utils
+/test-regex
 /test-run-command
 /test-sha1
 /test-sigchain
diff --git a/Makefile b/Makefile
index 3a1fe20..482b9f9 100644
--- a/Makefile
+++ b/Makefile
@@ -428,6 +428,7 @@ TEST_PROGRAMS_NEED_X += test-match-trees
 TEST_PROGRAMS_NEED_X += test-obj-pool
 TEST_PROGRAMS_NEED_X += test-parse-options
 TEST_PROGRAMS_NEED_X += test-path-utils
+TEST_PROGRAMS_NEED_X += test-regex
 TEST_PROGRAMS_NEED_X += test-run-command
 TEST_PROGRAMS_NEED_X += test-sha1
 TEST_PROGRAMS_NEED_X += test-sigchain
diff --git a/t/t0070-fundamental.sh b/t/t0070-fundamental.sh
index 9bee8bf..da2c504 100755
--- a/t/t0070-fundamental.sh
+++ b/t/t0070-fundamental.sh
@@ -25,4 +25,9 @@ test_expect_success POSIXPERM 'mktemp to unwritable directory prints filename' '
 	grep "cannotwrite/test" err
 '
 
+test_expect_success 'check for a bug in the regex routines' '
+	# if this test fails, re-build git with NO_REGEX=1
+	test-regex
+'
+
 test_done
diff --git a/test-regex.c b/test-regex.c
new file mode 100644
index 0000000..9259985
--- /dev/null
+++ b/test-regex.c
@@ -0,0 +1,35 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <sys/types.h>
+#include <regex.h>
+
+static void die(const char *fmt, ...)
+{
+	va_list p;
+
+	va_start(p, fmt);
+	vfprintf(stderr, fmt, p);
+	va_end(p);
+	fputc('\n', stderr);
+	exit(128);
+}
+
+int main(int argc, char **argv)
+{
+	char *pat = "[^={} \t]+";
+	char *str = "={}\nfred";
+	regex_t r;
+	regmatch_t m[1];
+
+	if (regcomp(&r, pat, REG_EXTENDED | REG_NEWLINE))
+		die("failed regcomp() for pattern '%s'", pat);
+	if (regexec(&r, str, 1, m, 0))
+		die("no match of pattern '%s' to string '%s'", pat, str);
+
+	/* http://sourceware.org/bugzilla/show_bug.cgi?id=3957  */
+	if (m[0].rm_so == 3) /* matches '\n' when it should not */
+		exit(1);
+
+	exit(0);
+}
-- 
1.7.5