| Message ID | ea451cae-782b-69ee-cff4-26b761f451fd@crans.org |
|---|---|
| State | New |
| Headers | show |
| Series | PR libstdc++/70664 Set failbit and read zero on stream reading negative value into unsigned type | expand |
On 13 March 2018 at 15:55, Jean-Baptiste Daval wrote: > Hi, > > Currently when a value is extracted from a stream into a unsigned type, > there is no test to check if the value is negative, in which case there > is an overflow and failbit is not set (the correct behavior would be to > read a zero and set failbit). This patch add a condition to check when > we are in this particular case, read a zero and set failbit accordingly. Thank you for the patch. It looks small enough that we don't need a copyright assignment. The GCC trunk is currently only open for regression fixes (and we also allow changes to C++17 library features while our C++17 support is considered experimental). As soon as the trunk re-opens for normal changes I'll apply your patch. For now I've updated the bug report with a link to your patch, so we won't forget about it.
--- a/libstdc++-v3/include/bits/locale_facets.tcc +++ b/libstdc++-v3/include/bits/locale_facets.tcc @@ -571,6 +571,11 @@ _GLIBCXX_BEGIN_NAMESPACE_LDBL __v = 0; __err = ios_base::failbit; } + else if (__negative && !__num_traits::_is_signed) + { + __v = 0; + __err = ios_base::failbit; + } else if (__testoverflow) { if (__negative && __num_traits::__is_signed)
Hi, Currently when a value is extracted from a stream into a unsigned type, there is no test to check if the value is negative, in which case there is an overflow and failbit is not set (the correct behavior would be to read a zero and set failbit). This patch add a condition to check when we are in this particular case, read a zero and set failbit accordingly. Tested on x86_64-pc-linux-gnu with the program provided in the bug report (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70664) #include <iostream> #include <sstream> using namespace std; template <typename T> void test(const char * str) { istringstream a(str); T i; a >> i; if (a.fail()) cout << "Ok: " << i << "\n"; else cout << "Bug: " << i << "\n"; } int main(int argc, char *argv[]) { test<int>("2147483648"); // INT_MIN-1 test<int>("-2147483649"); // INT_MAX+1 test<unsigned>("4294967296"); // UINT_MAX+1 test<unsigned>("-1"); return 0; } Output without the patch: Ok: 2147483647 Ok: -2147483648 Ok: 4294967295 Bug: 4294967295 With the patch: Ok: 2147483647 Ok: -2147483648 Ok: 4294967295 Ok: 0 libstdc++-v3/ChangeLog: 2018-03-13 Jean-Baptiste Daval <naarakah@crans.org> PR libstdc++/70664 * locale_facets_fix.tcc: Test when extracting a negative value into an unsigned type libstdc++-v3/include/bits/locale_facets.tcc | 5 +++++ 1 file changed, 5 insertions(+) iff --git a/libstdc++-v3/include/bits/locale_facets.tcc b/libstdc++-v3/include/bits/locale_facets.tcc index 39da5766075..9bc06c2e558 100644