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Work around incompatibility in <regex> in libc++

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libc++ (the implementation of the C++ standard library usually used by
Clang) throws an exception for the regex used by parse_headers before
this patch for certain strings. Work around this by simplifying the
regex and parsing the header lines "by hand" partially. I have repro'd
this problem with Xcode 11.1 which I believe uses libc++ version 8.

This may be a bug in libc++ as I can't see why the regex would result in
asymptotic run-time complexity for any strings. However, it may take a
while for libc++ to be fixed and for everyone to migrate to it, so it
makes sense to work around it in this codebase for now.
This commit is contained in:
Matthew DeVore 2019-12-02 13:38:56 -08:00
parent a9e942d755
commit bc9251ea49
2 changed files with 73 additions and 22 deletions
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20
httplib.h
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@ -1566,7 +1566,7 @@ inline bool read_headers(Stream &strm, Headers &headers) {
// the left or right side of the header value:
// - https://stackoverflow.com/questions/50179659/
// - https://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html
static std::regex re(R"((.+?):[\t ]*(.+?)[\t ]*\r\n)");
static std::regex re(R"((.+?):[\t ]*(.+))");
const auto bufsiz = 2048;
char buf[bufsiz];
@ -1575,9 +1575,23 @@ inline bool read_headers(Stream &strm, Headers &headers) {
for (;;) {
if (!line_reader.getline()) { return false; }
if (!strcmp(line_reader.ptr(), "\r\n")) { break; }
const char *end = line_reader.ptr() + line_reader.size();
auto erase_last_char = [&](char c) {
if (line_reader.ptr() == end || end[-1] != c) {
return false;
}
end--;
return true;
};
if (!erase_last_char('\n')) { continue; }
if (!erase_last_char('\r')) { continue; }
// Blank line indicates end of headers.
if (line_reader.ptr() == end) { break; }
while (erase_last_char(' ') || erase_last_char('\t')) {}
std::cmatch m;
if (std::regex_match(line_reader.ptr(), m, re)) {
if (std::regex_match(line_reader.ptr(), end, m, re)) {
auto key = std::string(m[1]);
auto val = std::string(m[2]);
headers.emplace(key, val);