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size tilde code fences by the longest tilde run in commonmark renderer #645

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Merged
jgm merged 1 commit into from
Oct 21, 2026
Merged

size tilde code fences by the longest tilde run in commonmark renderer #645

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15 changes: 15 additions & 0 deletions api_test/main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -804,6 +804,21 @@ static void render_commonmark(test_batch_runner *runner) {
free(commonmark);
cmark_node_free(plain_break_doc);

// An info string containing a backtick forces a tilde fence, which must
// be longer than any run of tildes in the code.
static const char tilde_fence[] = "~~~~~ a`b\n"
"~~~\n"
"<b>x</b>\n"
"~~~~~\n";
cmark_node *tilde_fence_doc =
cmark_parse_document(tilde_fence, sizeof(tilde_fence) - 1,
CMARK_OPT_DEFAULT);
commonmark = cmark_render_commonmark(tilde_fence_doc, CMARK_OPT_DEFAULT, 0);
STR_EQ(runner, commonmark, "~~~~ a`b\n~~~\n<b>x</b>\n~~~~\n",
"render tilde fence longer than tildes in code");
free(commonmark);
cmark_node_free(tilde_fence_doc);

cmark_node_free(text);
cmark_node_free(doc);
}
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6 changes: 3 additions & 3 deletions src/commonmark.c
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Original file line number Diff line number Diff line change
Expand Up @@ -73,13 +73,13 @@ static inline void outc(cmark_renderer *renderer, cmark_escaping escape,
}
}

static int longest_backtick_sequence(const char *code) {
static int longest_char_sequence(const char *code, char c) {
int longest = 0;
int current = 0;
size_t i = 0;
size_t code_len = strlen(code);
while (i <= code_len) {
if (code[i] == '`') {
if (code[i] == c) {
current++;
} else {
if (current > longest) {
Expand Down Expand Up @@ -281,7 +281,7 @@ static int S_render_node(cmark_renderer *renderer, cmark_node *node,
fencechar[0] = strchr(info, '`') == NULL ? '`' : '~';
code = cmark_node_get_literal(node);

numticks = longest_backtick_sequence(code) + 1;
numticks = longest_char_sequence(code, fencechar[0]) + 1;
if (numticks < 3) {
numticks = 3;
}
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