Re: A little more progress today with clang/LLVM

[Szabolcs Nagy <nsz@port70.net>]

* Richard Pennington <rich@pennware.com> [2012-05-26 06:39:25 -0500]:
> My tgmath.h test cases fail, for example (f is a float, d is a double):
> 

tgmath.h is non-trivial and is not extensively tested so there can be issues

> ../../../../../src/libs/math/001tgmath.c:15:7: error: assigning to 'float' from 
> incompatible type 'typeof (*(0
>       ? (typeof (0 ? (double *)0 : (void *)!!((1 ? 1 : ((f))) / 2)))0 : 
> (typeof (0 ? (typeof ((f)) *)0 :
>       (void *)!!!((1 ? 1 : ((f))) / 2)))0))' (aka 'void')

sounds like a clang bug

this code is marked with #ifdef __GNUC__ and
uses __typeof__ and ?: trics to be able to cast
the return value to the correct type


to try the messy expression above in isolation you can use:

#define T __typeof__
#define ISFP(x) !!((1?1:(x))/2)

float f = 0.1;
T(*(0 ? (T(0 ? (double *)0 : (void *)ISFP(f)))0 :
        (T(0 ? (T(f) *)0 : (void *)!ISFP(f)))0)) *x = &f;


but i think clang gets the ?: thing wrong
eg. try

__typeof__(0 ? (char*)0 : (void*)1) p;
void **pp = &p;

__typeof__(0 ? (char*)0 : (void*)0) q;
char **qq = &q;


(this should compile cleanly)