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Fix stack-use-after-return with unterminated heredocs #4155

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Fix stack-use-after-return with unterminated heredocs #4155

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10 changes: 10 additions & 0 deletions src/prism.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19712,6 +19712,16 @@ parse_expression_prefix(pm_parser_t *parser, pm_binding_power_t binding_power, u
}
}

// If a missing terminator left this heredoc's lex mode on the
// stack, it still points at our stack-local common_whitespace.
// Clear the pointer so that subsequent lexing cannot read from
// this function's dead stack frame.
for (pm_lex_mode_t *mode = parser->lex_modes.current; mode != NULL; mode = mode->prev) {
if (mode->mode == PM_LEX_HEREDOC && mode->as.heredoc.common_whitespace == &common_whitespace) {
mode->as.heredoc.common_whitespace = NULL;
}
}

if (match1(parser, PM_TOKEN_STRING_BEGIN)) {
return parse_strings(parser, node, false, (uint16_t) (depth + 1));
}
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