https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93410
Bug ID: 93410 Summary: can't use _Decimal64 in C99/C11/C17 mode Product: gcc Version: 9.2.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: vincent-gcc at vinc17 dot net Target Milestone: --- With GCC 9.2.1 under Debian/unstable (x86_64): cventin% cat tst.c int main (void) { _Decimal64 x = 1; return x != 1; } cventin% gcc-9 tst.c -o tst cventin% but cventin% gcc-9 -std=c99 tst.c -o tst tst.c: In function ‘main’: tst.c:3:3: error: unknown type name ‘_Decimal64’ 3 | _Decimal64 x = 1; | ^~~~~~~~~~ cventin% gcc-9 -std=c11 tst.c -o tst tst.c: In function ‘main’: tst.c:3:3: error: unknown type name ‘_Decimal64’ 3 | _Decimal64 x = 1; | ^~~~~~~~~~ cventin% gcc-9 -std=c17 tst.c -o tst tst.c: In function ‘main’: tst.c:3:3: error: unknown type name ‘_Decimal64’ 3 | _Decimal64 x = 1; | ^~~~~~~~~~ cventin% There is no such issue with the trunk (where one just gets a warning if -pedantic is used, which is expected).