Re: [PATCH 3/3] grep: get rid of useless x < 0 comparison on an enum member

Hi,

I imagine the following would be less controversial.

-- >8 --
From: Ævar Arnfjörð Bjarmason <redacted>
Subject: grep: get rid of bounds check on "enum grep_header_field" value

The grep_header_field enum is defined as:

    enum grep_header_field {
    	GREP_HEADER_AUTHOR = 0,
    	GREP_HEADER_COMMITTER
    };

Git's grep code sanity-checks the value of p->field before using it in
order to avoid reading and writing past the end of an array.
Unfortunately that test trips up misguided static analyzers like
"gcc -Wtype-limits" that do not recognize that C allows this enum to
be a signed integer type and an "x < 0" comparison really could fire
if someone passed in an uninitialized value.

Let's just drop the check.  Luckily git always does initialize
p->field correctly, and if it were to stop doing so, then hopefully
running the test suite with valgrind would catch it.

Noticed with clang -Wtautological-compare.

[jn: drop the GREP_HEADER_FIELD_MAX <= p->field check, too,
 for symmetry]

Signed-off-by: Ævar Arnfjörð Bjarmason <redacted>
Signed-off-by: Jonathan Nieder <redacted>
---
 grep.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/grep.c b/grep.c
index b29d09c7..424c46cd 100644
--- a/grep.c
+++ b/grep.c

@@ -327,8 +327,6 @@ static struct grep_expr *prep_header_patterns(struct grep_opt *opt)
 	for (p = opt->header_list; p; p = p->next) {
 		if (p->token != GREP_PATTERN_HEAD)
 			die("bug: a non-header pattern in grep header list.");
-		if (p->field < 0 || GREP_HEADER_FIELD_MAX <= p->field)
-			die("bug: unknown header field %d", p->field);
 		compile_regexp(p, opt);
 	}
 

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1.7.8.rc0