On 2021-01-03 21:17:03 +0200, Arnold Robbins wrote:
> Hi.
>
> I found this bug in current mob on the current gawk sources. Test case:
>
> -----------------------------
> #include <stdio.h>
> #include <math.h>
> #include <stdlib.h>
>
> int main(int argc, char **argv)
> {
> double d = strtod("-nan", NULL);
> d = -d;
> printf("%g, signbit(d) = %d\n", d, signbit(d));
> return 0;
> }
> -----------------------------
>
> Results:
>
> $ gcc foo.c -o foo && ./foo
> -nan, signbit(d) = 1
>
> $ tcc foo.c -o foo2 && ./foo2
> nan, signbit(d) = 0
>
> I get the same results as gcc with clang and pcc. tcc is the outlier.
AFAIK, the status of the sign bit of a NaN is unspecified, except
for some particular functions, but not strtod. So I don't see a
bug in tcc.
Note: for GCC, there's an inconsistency between your testcase
and the result.
--
Vincent Lefèvre <[email protected]> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
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