I've submitted 207175 for a clang 3.8.0 va_list handling problem for powerpc

[Mark Millard]

I've isolated another clang 3.8.0 TARGET_ARCH=powerpc SEGV problem that shows up for using clang 3.8.0 to buildworld/installworld for powerpc.

> ls -l -n /

gets a SEGV. As listed in https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=207175 ( and  https://llvm.org/bugs/show_bug.cgi?id=26605 ) the following simplified program also gets the SEGV on powerpc:

> #include <stdarg.h> // for va_list, va_start, va_arg, va_end
> #include <stdint.h> // for intmax_t
> 
> intmax_t
> va_test (char *s, ...)
> {
>     va_list vap;
> 
>     va_start(vap, s);
> 
>     char*        t0 = va_arg(vap, char*);
>     unsigned int o0 = va_arg(vap, unsigned int);
>     int          c0 = va_arg(vap, int);
>     unsigned int u0 = va_arg(vap, unsigned int);
>     int          c1 = va_arg(vap, int);
>     char *       t1 = va_arg(vap, char*);
>  
>     intmax_t     j0 = va_arg(vap, intmax_t); // This spans into overflow_arg_area.
> 
>     int          c2 = va_arg(vap, int);      // A copy was put in the 
>                                              // overflow_arg_area because of the
>                                              // above.
>                                              // But this tries to extract from the
>                                              // last 4 bytes of the reg_save_area.
>                                              // It does not increment the
>                                              // overflow_arg_area position pointer
>                                              // past the copy that is there.
> 
>     char *       t2 = va_arg(vap, char*);    // The lack of increment before makes
>                                              // this extraction off by 4 bytes.
> 
>     char         t2fc = *t2;  // <<< This gets SEGV. t2 actually got what should be
>                               //     the c2 value.
> 
>     intmax_t     j1 = va_arg(vap, intmax_t);
> 
>     va_end(vap);
> 
>     return (intmax_t) ((s-t2)+(t0-t1)+o0+u0+j0+j1+c0+c1+c2+t2fc);
>     // Avoid any optimize-away for lack of use.
> }
> 
> int main(void)
> {
>     char         s[1025] = "test string for this";
> 
>     char*        t0 = s + 5;
>     unsigned int o0 = 3;
>     int          c0 = 1;
>     unsigned int u0 = 1;
>     int          c1 = 3;
>     char *       t1 = s + 12;
>     intmax_t     j0 = 314159265358979323;
>     int          c2 = 4;
>     char *       t2 = s + 16;
>     intmax_t     j1 = ~314159265358979323;
> 
>     intmax_t      result = va_test(s,t0,o0,c0,u0,c1,t1,j0,c1,t2,j1);
> 
>     return (int) (result - (intmax_t) ((s-t2)+(t0-t1)+o0+u0+j0+j1+c0+c1+c2+*t2));
>     // Avoid any optimize-away for lack of use.
> }



===
Mark Millard
markmi at dsl-only.net