line-range: fix infinite loop bug with '$' regex

When the -L argument to "git log" is passed the zero-width regular
expression "$" (as in "-L :$:line-range.c"), this results in an
infinite loop in find_funcname_matching_regexp().

Modify find_funcname_matching_regexp to correctly match the entire line
instead of the zero-width match at eol and update the loop condition to
prevent an infinite loop in the event of other undiscovered corner cases.

The primary change is that we pre-decrement the beginning-of-line marker
('bol') before comparing it to '\n'. In the case of '$', where we match the
'\n' at the end of the line and start the loop with bol == eol, this
ensures that bol will find the beginning of the line on which the match
occurred.

Originally reported in <https://stackoverflow.com/q/74690545/147356>.

Signed-off-by: Lars Kellogg-Stedman <lars@oddbit.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/line-range.c b/line-range.c
index 955a8a9535575fe0a397497d765f3e0e97334259..47bf0d6f1a253a01baf6e3d0f68dfa5d5df6a0f0 100644 (file)
--- a/line-range.c
+++ b/line-range.c
@@ -135,7 +135,7 @@ static const char *find_funcname_matching_regexp(xdemitconf_t *xecfg, const char
 {
        int reg_error;
        regmatch_t match[1];
-       while (1) {
+       while (*start) {
                const char *bol, *eol;
                reg_error = regexec(regexp, start, 1, match, 0);
                if (reg_error == REG_NOMATCH)
@@ -148,8 +148,8 @@ static const char *find_funcname_matching_regexp(xdemitconf_t *xecfg, const char
                /* determine extent of line matched */
                bol = start+match[0].rm_so;
                eol = start+match[0].rm_eo;
-               while (bol > start && *bol != '\n')
-                       bol--;
+               while (bol > start && *--bol != '\n')
+                       ; /* nothing */
                if (*bol == '\n')
                        bol++;
                while (*eol && *eol != '\n')
@@ -161,6 +161,7 @@ static const char *find_funcname_matching_regexp(xdemitconf_t *xecfg, const char
                        return bol;
                start = eol;
        }
+       return NULL;
 }
 
 static const char *parse_range_funcname(

diff --git a/t/t4211-line-log.sh b/t/t4211-line-log.sh
index ac9e4d0928593cd37b4a79e27f5fe99b6e4a3faf..c6540e822fbdc56f068ae1b8d991175303bff038 100755 (executable)
--- a/t/t4211-line-log.sh
+++ b/t/t4211-line-log.sh
@@ -315,4 +315,26 @@ test_expect_success 'line-log with --before' '
        test_cmp expect actual
 '
 
+test_expect_success 'setup tests for zero-width regular expressions' '
+       cat >expect <<-EOF
+       Modify func1() in file.c
+       Add func1() and func2() in file.c
+       EOF
+'
+
+test_expect_success 'zero-width regex $ matches any function name' '
+       git log --format="%s" --no-patch "-L:$:file.c" >actual &&
+       test_cmp expect actual
+'
+
+test_expect_success 'zero-width regex ^ matches any function name' '
+       git log --format="%s" --no-patch "-L:^:file.c" >actual &&
+       test_cmp expect actual
+'
+
+test_expect_success 'zero-width regex .* matches any function name' '
+       git log --format="%s" --no-patch "-L:.*:file.c" >actual &&
+       test_cmp expect actual
+'
+
 test_done