https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120548
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
So the fix needs to also check for a leading ' ' as the sign character:
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -2398,9 +2398,16 @@ namespace __format
const size_t __r = __str.size() - __e; // Length of remainder.
auto __overwrite = [&](_CharT* __p, size_t) {
// Apply grouping to the digits before the radix or exponent.
- auto __end = std::__add_grouping(__p, __np.thousands_sep(),
+ int __off = 0;
+ if (auto __c = __str.front(); __c == '-' || __c == '+' || __c == ' ')
+ {
+ *__p = __c;
+ __off = 1;
+ }
+ auto __end = std::__add_grouping(__p + __off, __np.thousands_sep(),
__grp.data(), __grp.size(),
- __str.data(), __str.data() + __e);
+ __str.data() + __off,
+ __str.data() + __e);
if (__r) // If there's a fractional part or exponent
{
if (__d != __str.npos)
