Re: [Tinycc-devel] Annoying new warning

[Michael Matz]

Hi,

On Sat, 29 Apr 2017, Christian Jullien wrote:

> No one looking at it? What is the behavior of this test when lower is 
> unitialized?

As the comment above the structure clearly says, this is the layout for 
x86 only (the x87 80bit long double type).  ARMs long double type simply 
is double itself, and hence these functions are unused on ARM.  Well, they 
would be if there wouldn't be strange code in arm-gen.c that makes use of 
xfdi conversions when VFP is enabled.  That makes no sense, also with VFP 
there's only support for IEEE double, not for extended double.

So the fix for this would entail ifdefing the XF routines in libtcc1.c, 
and not using them in the arm backend.


Ciao,
Michael.

 > 
>  
>
> From:  Christian JULLIEN
>
>   Subject:  [Tinycc-devel] Annoying new warning
>
> Date:  Thu, 20 Apr 2017 09:29:31 +0200 (CEST)
>
>  
>
> Trying to build mob on RPI I now get this new warning
>
>  
>
> gcc -c ./lib/libtcc1.c -o libtcc1.o -DTCC_TARGET_ARM -Wall -g -O2
> -Wdeclaration-after-statement -Wno-pointer-sign -Wno-sign-compare
> -Wno-unused-result -fno-strict-aliasing -I.  -fPIC
>
> ./lib/libtcc1.c: In function __fixunsxfdi:
>
> ./lib/libtcc1.c:586:26: warning: dl1.l.upper is used uninitialized in this
> function [-Wuninitialized]
>
>      if (dl1.l.lower == 0 && dl1.l.upper == 0)
>
>                           ^
>
>  
>
> unsigned long long __fixunsxfdi (long double a1)
>
> {
>
>     register union ldouble_long dl1;
>
>     register int exp;
>
>     register unsigned long long l;
>
>  
>
>     dl1.ld = a1;
>
>  
>
>     if (dl1.l.lower == 0 && dl1.l.upper == 0)
>
>         return (0);
>
>  
>
>  
>
> And union is defined as:
>
>  
>
> /* only for x86 */
>
> union ldouble_long {
>
>     long double ld;
>
>     struct {
>
>         unsigned long long lower;
>
>         unsigned short upper;
>
>     } l;
>
> };