Escape \end{verbatim} inside latex code blocks

api_test/main.c

@@ -717,6 +717,26 @@ static void render_latex(test_batch_runner *runner) {
          "enumerate counter ignores bullet list nesting");
   free(latex);
   cmark_node_free(nested_doc);
+
+  // A code block containing \end{verbatim} must not close the verbatim
+  // environment and let the following lines be read as LaTeX.
+  static const char code[] = "    a\n"
+                             "    \\end{verbatim}\n"
+                             "    \\input{secret}\n";
+  cmark_node *code_doc =
+      cmark_parse_document(code, sizeof(code) - 1, CMARK_OPT_DEFAULT);
+  latex = cmark_render_latex(code_doc, CMARK_OPT_DEFAULT, 0);
+  STR_EQ(runner, latex,
+         "\\begin{verbatim}\n"
+         "a\n"
+         "\\end{verbatim}\n"
+         "\\texttt{\\textbackslash{}end\\{verbatim\\}}\n"
+         "\\begin{verbatim}\n"
+         "\\input{secret}\n"
+         "\\end{verbatim}\n",
+         "escape \\end{verbatim} inside code block");
+  free(latex);
+  cmark_node_free(code_doc);
 }
 
 static void render_commonmark(test_batch_runner *runner) {

src/latex.c

@@ -217,6 +217,36 @@ static int S_get_enumlevel(cmark_node *node) {
   return enumlevel;
 }
 
+// A literal \end{verbatim} would close the environment early and the
+// rest of the code block would be read as LaTeX, so close the environment
+// before each occurrence, print it escaped, and reopen.
+static void S_render_verbatim(cmark_renderer *renderer, const char *code) {
+  static const char end_verbatim[] = "\\end{verbatim}";
+  const char *match;
+  cmark_strbuf buf = CMARK_BUF_INIT(renderer->mem);
+
+  while ((match = strstr(code, end_verbatim)) != NULL) {
+    cmark_strbuf_set(&buf, (const unsigned char *)code,
+                     (bufsize_t)(match - code));
+    OUT((const char *)buf.ptr, false, LITERAL);
+    CR();
+    LIT("\\end{verbatim}");
+    CR();
+    LIT("\\texttt{");
+    OUT(end_verbatim, false, NORMAL);
+    LIT("}");
+    CR();
+    LIT("\\begin{verbatim}");
+    CR();
+    code = match + sizeof(end_verbatim) - 1;
+    if (*code == '\n') {
+      code++;
+    }
+  }
+  OUT(code, false, LITERAL);
+  cmark_strbuf_free(&buf);
+}
+
 static int S_render_node(cmark_renderer *renderer, cmark_node *node,
                          cmark_event_type ev_type, int options) {
   int list_number;
@@ -318,7 +348,7 @@ static int S_render_node(cmark_renderer *renderer, cmark_node *node,
     CR();
     LIT("\\begin{verbatim}");
     CR();
-    OUT(cmark_node_get_literal(node), false, LITERAL);
+    S_render_verbatim(renderer, cmark_node_get_literal(node));
     CR();
     LIT("\\end{verbatim}");
     BLANKLINE();