[cfe-dev] interesting clang issue with "floor"

[reed kotler]

Maybe there is some special C rule here that  I don't understand but I 
am declaring floor and floor_.

consider floor1.c

extern double floor(double);
extern double floor_(double);

double x = 1.5;
double y, y_;

void foo() {

   y = floor(x);
   y_ = floor_(x);
}


and floor.c

#include <stdio.h>

extern double x, y, y_;

double floor(double x) {
   return 2*x;
}

double floor_(double x) {
   return 3*x;
}

extern void foo();

int main() {
   foo();
   printf("%e %e %e \n", x, y, y_);
   return 0;
}

  /local/llvmpb_config/install/bin/clang floor1.c floor.c

rkotler at ubuntu-rkotler:~/testmips16$ ./a.out
1.500000e+00 3.000000e+00 4.500000e+00





On 07/26/2013 06:14 PM, Richard Smith wrote:
> On Fri, Jul 26, 2013 at 6:05 PM, reed kotler <rkotler at mips.com 
> <mailto:rkotler at mips.com>> wrote:
>
>     I'm chasing down another issue with floor in llvm but noticed this
>     strange behavior:
>
>     Consider the following code:
>
>     extern double floor(double);
>     extern double floor_(double);
>
>     double x = 1.5;
>     double y, y_;
>
>     void foo() {
>
>       double y = floor(x);
>       double y_ = floor_(x);
>     }
>
>
>      /local/llvmpb_config/install/bin/clang floor1.c -o floor1.llc
>     -emit-llvm -S
>
>     The attributes for floor and floor_ are different.
>
>
> This is expected; we recognise 'floor' as a builtin.

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