https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84764
Bug ID: 84764
Summary: Wrong warning "so large that it is unsigned" for
__int128 constant
Product: gcc
Version: 7.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: pascal_cuoq at hotmail dot com
Target Milestone: ---
According to the output of the following program, the type of the constant
10000000000000000000 is __int128, which is a signed type:
Compiler Explorer link: https://godbolt.org/g/kFTNaz
#include <stdio.h>
#define prtype(X) \
_Generic((X), \
int: "int", \
long: "long", \
long long: "long long", \
unsigned int: "unsigned int", \
unsigned long: "unsigned long", \
unsigned long long: "unsigned long long", \
__int128: "__int128", \
default: "?")
int main(void) {
printf("1 %s\n", prtype(1));
printf("3000000000 %s\n", prtype(3000000000));
printf("10000000000000000000 %s\n", prtype(10000000000000000000));
}
___
Output:
1 int
3000000000 long
10000000000000000000 __int128
However a warning is emitted on the last line for the constant
10000000000000000000:
prtype.c:17:66: warning: integer constant is so large that it is unsigned
This warning implies that the constant is typed as long long, which has been
the case either historically or with other -std= settings. However, for the
compilation settings at hand, the warning is wrong. It should at most say that
the constant is typed with a type outside of the "int, long, long long"
hierarchy of standard types.
For reference the relevant clause of the C11 standard is 6.4.4:
https://port70.net/~nsz/c/c11/n1570.html#6.4.4
