https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81021
Bug ID: 81021
Summary: stack-use-after-scope false positive error with
exceptions
Product: gcc
Version: 7.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: sanitizer
Assignee: unassigned at gcc dot gnu.org
Reporter: matt at godbolt dot org
CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org,
jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at
gcc dot gnu.org
Target Milestone: ---
GCC 7.1 compiled from source, testing on Ubuntu and Arch linux.
The following minimal reproduction code:
---snip---
#include <string>
struct ConfigFile {
ConfigFile(std::string filename, std::string delimiter) { throw "error"; }
};
struct Configuration {
ConfigFile _configFile;
Configuration(const std::string &root, const char *baseName)
: _configFile(root + baseName, "=") { }
};
void test() {
std::string root("etc");
try {
Configuration config(root, "notthere");
}
catch (...) {
// exception is thrown, caught here and ignored...
}
Configuration config(root, "sample"); // ASAN error during constructor here
}
int main(int argc, const char *argv[]) {
test();
}
---snip---
when compiled and run with the address sanitizer with `g++ -fsanitize=address
test.cc -o test` gives the following apparent false positive.
=================================================================
==44114==ERROR: AddressSanitizer: stack-use-after-scope on address
0x7ffd3b2bf6f0 at pc 0x0000004fa7bf bp 0x7ffd3b2bf660 sp 0x7ffd3b2bf658
WRITE of size 32 at 0x7ffd3b2bf6f0 thread T0
#0 0x4fa7be in
Configuration::Configuration(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > const&, char const*)
(/home/mgodbolt/dev/gcc7-bug/test+0x4fa7be)
#1 0x4fa4b9 in test() (/home/mgodbolt/dev/gcc7-bug/test+0x4fa4b9)
#2 0x4fa5de in main (/home/mgodbolt/dev/gcc7-bug/test+0x4fa5de)
#3 0x2b6b74945f44 in __libc_start_main
(/lib/x86_64-linux-gnu/libc.so.6+0x21f44)
#4 0x405ebb (/home/mgodbolt/dev/gcc7-bug/test+0x405ebb)
Address 0x7ffd3b2bf6f0 is located in stack of thread T0 at offset 96 in frame
#0 0x4fa689 in
Configuration::Configuration(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > const&, char const*)
(/home/mgodbolt/dev/gcc7-bug/test+0x4fa689)
This frame has 3 object(s):
[32, 33) '<unknown>'
[96, 128) '<unknown>' <== Memory access at offset 96 is inside this
variable
[160, 192) '<unknown>'
HINT: this may be a false positive if your program uses some custom stack
unwind mechanism or swapcontext
(longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-use-after-scope
(/home/mgodbolt/dev/gcc7-bug/test+0x4fa7be) in
Configuration::Configuration(std::__cxx11::basic_string<char,
std::char_traits<char>, std::allocator<char> > const&, char const*)
Shadow bytes around the buggy address:
0x10002764fe80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10002764fe90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10002764fea0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10002764feb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10002764fec0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x10002764fed0: 00 00 f1 f1 f1 f1 01 f2 f2 f2 f2 f2 f2 f2[f8]f8
0x10002764fee0: f8 f8 f2 f2 f2 f2 f8 f8 f8 f8 f3 f3 f3 f3 00 00
0x10002764fef0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10002764ff00: 00 00 f8 00 00 00 00 00 00 00 01 00 00 00 00 00
0x10002764ff10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10002764ff20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Reducing the file further (removing the apparently unnecessary std::strings)
prevents this issue from being flagged up.
