Reduction of issue with PR implement URLPattern #785

[lemire]

There is an issue with GCC in PR #785

We can reproduce it with a simple case. This is the test:

#include "ada.h"



bool test() {
  auto tokenize_result = ada::url_pattern_helpers::tokenize();
  return tokenize_result.empty();
}

int main() {
    test();
    return EXIT_SUCCESS;
}

The tokenize function is declared like so:

#ifndef ADA_URL_PATTERN_HELPERS_H
#define ADA_URL_PATTERN_HELPERS_H

#include <vector>

namespace ada::url_pattern_helpers {
std::vector<int> tokenize();
}  // namespace ada::url_pattern_helpers
#endif

It is then defined like so:

#include "ada/url_pattern_helpers.h"

namespace ada::url_pattern_helpers {

std::vector<int> tokenize() {
  std::vector<int> token_list;
  return token_list;
}

}  // namespace ada::url_pattern_helpers

Running the test with sanitizers, I get...

$ ./simple_wpt_urlpattern_tests 
=================================================================
==2613422==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7f10f1d00038 at pc 0x0000004eb025 bp 0x7fff461aab60 sp 0x7fff461aab50
WRITE of size 8 at 0x7f10f1d00038 thread T0
    #0 0x4eb024 in std::__cxx1998::_Vector_base<int, std::allocator<int> >::_Vector_impl_data::_Vector_impl_data() /opt/rh/gcc-toolset-12/root/usr/include/c++/12/bits/stl_vector.h:100
    #1 0x4dc487 in std::__cxx1998::_Vector_base<int, std::allocator<int> >::_Vector_impl::_Vector_impl() /opt/rh/gcc-toolset-12/root/usr/include/c++/12/bits/stl_vector.h:139
    #2 0x494679 in std::__cxx1998::_Vector_base<int, std::allocator<int> >::_Vector_base() /opt/rh/gcc-toolset-12/root/usr/include/c++/12/bits/stl_vector.h:312
    #3 0x494695 in std::__cxx1998::vector<int, std::allocator<int> >::vector() /opt/rh/gcc-toolset-12/root/usr/include/c++/12/bits/stl_vector.h:526
    #4 0x4946c1 in std::__debug::vector<int, std::allocator<int> >::vector() /opt/rh/gcc-toolset-12/root/usr/include/c++/12/debug/vector:172
    #5 0x43b33b in ada::url_pattern_helpers::tokenize() /home/dlemire/CVS/github/ada/src/url_pattern_helpers.cpp:6
    #6 0x4057ed in test() /home/dlemire/CVS/github/ada/tests/simple_wpt_urlpattern_tests.cpp:8
    #7 0x405871 in main /home/dlemire/CVS/github/ada/tests/simple_wpt_urlpattern_tests.cpp:13
    #8 0x7f10f3a295cf in __libc_start_call_main (/lib64/libc.so.6+0x295cf) (BuildId: d78a44ae94f1d320342e0ff6c2315b2b589063f8)
    #9 0x7f10f3a2967f in __libc_start_main@GLIBC_2.2.5 (/lib64/libc.so.6+0x2967f) (BuildId: d78a44ae94f1d320342e0ff6c2315b2b589063f8)
    #10 0x405634 in _start (/mnt/bigdisk/lemire/github/ada/buildsani/tests/simple_wpt_urlpattern_tests+0x405634) (BuildId: 63c849374513aff6d6749b6abde45b3df2b572f1)

Address 0x7f10f1d00038 is located in stack of thread T0 at offset 56 in frame
    #0 0x405705 in test() /home/dlemire/CVS/github/ada/tests/simple_wpt_urlpattern_tests.cpp:7

  This frame has 1 object(s):
    [32, 56) 'tokenize_result' (line 8) <== Memory access at offset 56 overflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow /opt/rh/gcc-toolset-12/root/usr/include/c++/12/bits/stl_vector.h:100 in std::__cxx1998::_Vector_base<int, std::allocator<int> >::_Vector_impl_data::_Vector_impl_data()
Shadow bytes around the buggy address:
  0x7f10f1cffd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7f10f1cffe00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7f10f1cffe80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7f10f1cfff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7f10f1cfff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x7f10f1d00000: f1 f1 f1 f1 00 00 00[f3]f3 f3 f3 f3 00 00 00 00
  0x7f10f1d00080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7f10f1d00100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7f10f1d00180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7f10f1d00200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7f10f1d00280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==2613422==ABORTING

[anonrig]

what happens if you return std::move(token_list) here? @jasnell's recommendation

[lemire]

Solved by @guidovranken and @pdimov