grep.c: remove "extended" in favor of "pattern_expression", fix segfault
Since 79d3696cfb4 (git-grep: boolean expression on pattern matching.,
2006-06-30) the "pattern_expression" member has been used for complex
queries (AND/OR...), with "pattern_list" being used for the simple OR
queries. Since then we've used both "pattern_expression" and its
associated boolean "extended" member to see if we have a complex
expression.
Since f41fb662f57 (revisions API: have release_revisions() release
"grep_filter", 2022-04-13) we've had a subtle bug relating to that: If
we supplied options that were only used for "complex queries", but
didn't supply the query itself we'd set "opt->extended", but would
have a NULL "pattern_expression". As a result these would segfault as
we tried to call "free_grep_patterns()" from "release_revisions()":
git -P log -1 --invert-grep
git -P log -1 --all-match
The root cause of this is that we were conflating the state management
we needed in "compile_grep_patterns()" itself with whether or not we
had an "opt->pattern_expression" later on.
In this cases as we're going through "compile_grep_patterns()" we have
no "opt->pattern_list" but have "opt->no_body_match" or
"opt->all_match". So we'd set "opt->extended = 1", but not "return" on
"opt->extended" as that's an "else if" in the same "if" statement.
That behavior is intentional and required, as the common case is that
we have an "opt->pattern_list" that we're about to parse into the
"opt->pattern_expression".
But we don't need to keep track of this "extended" flag beyond the
state management in compile_grep_patterns() itself. It needs it, but
once we're out of that function we can rely on
"opt->pattern_expression" being non-NULL instead for using these
extended patterns.
As 79d3696cfb4 itself shows we've assumed that there's a one-to-one
mapping between the two since the very beginning. I.e. "match_line()"
would check "opt->extended" to see if it should call "match_expr()",
and the first thing we do in that function is assume that we have a
"opt->pattern_expression". We'd then call "match_expr_eval()", which
would have died if that "opt->pattern_expression" was NULL.
The "die" was added in c922b01f54c (grep: fix segfault when "git grep
'('" is given, 2009-04-27), and can now be removed as it's now clearly
unreachable. We still do the right thing in the case that prompted
that fix:
git grep '('
fatal: unmatched parenthesis
Arguably neither the "--invert-grep" option added in [1] nor the
earlier "--all-match" option added in [2] were intended to be used
stand-alone, and another approach[3] would be to error out in those
cases. But since we've been treating them as a NOOP when given without
--grep for a long time let's keep doing that.
We could also return in "free_pattern_expr()" if the argument is
non-NULL, as an alternative fix for this segfault does [4]. That would
be more elegant in making the "free_*()" function behave like
"free()", but it would also remove a sanity check: The
"free_pattern_expr()" function calls itself recursively, and only the
top-level is allowed to be NULL, let's not conflate those two
conditions.
1. 22dfa8a23de (log: teach --invert-grep option, 2015-01-12)
2. 0ab7befa31d (grep --all-match, 2006-09-27)
3. https://lore.kernel.org/git/patch-1.1-f4b90799fce-20221010T165711Z-avarab@gmail.com/
4. http://lore.kernel.org/git/7e094882c2a71894416089f894557a9eae07e8f8.1665423686.git.me@ttaylorr.com
Reported-by: orygaw <orygaw@protonmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/grep.c b/grep.c
index 82eb7da..27e1db0 100644
--- a/grep.c
+++ b/grep.c
@@ -708,6 +708,7 @@ void compile_grep_patterns(struct grep_opt *opt)
{
struct grep_pat *p;
struct grep_expr *header_expr = prep_header_patterns(opt);
+ int extended = 0;
for (p = opt->pattern_list; p; p = p->next) {
switch (p->token) {
@@ -717,14 +718,14 @@ void compile_grep_patterns(struct grep_opt *opt)
compile_regexp(p, opt);
break;
default:
- opt->extended = 1;
+ extended = 1;
break;
}
}
if (opt->all_match || opt->no_body_match || header_expr)
- opt->extended = 1;
- else if (!opt->extended)
+ extended = 1;
+ else if (!extended)
return;
p = opt->pattern_list;
@@ -790,7 +791,7 @@ void free_grep_patterns(struct grep_opt *opt)
free(p);
}
- if (!opt->extended)
+ if (!opt->pattern_expression)
return;
free_pattern_expr(opt->pattern_expression);
}
@@ -971,8 +972,6 @@ static int match_expr_eval(struct grep_opt *opt, struct grep_expr *x,
{
int h = 0;
- if (!x)
- die("Not a valid grep expression");
switch (x->node) {
case GREP_NODE_TRUE:
h = 1;
@@ -1052,7 +1051,7 @@ static int match_line(struct grep_opt *opt,
struct grep_pat *p;
int hit = 0;
- if (opt->extended)
+ if (opt->pattern_expression)
return match_expr(opt, bol, eol, ctx, col, icol,
collect_hits);
@@ -1370,7 +1369,7 @@ static int should_lookahead(struct grep_opt *opt)
{
struct grep_pat *p;
- if (opt->extended)
+ if (opt->pattern_expression)
return 0; /* punt for too complex stuff */
if (opt->invert)
return 0;
