[llvm-bugs] [Bug 46810] New: Missing inexact FP exception on cast

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46810

            Bug ID: 46810
           Summary: Missing inexact FP exception on cast
           Product: clang
           Version: 10.0
          Hardware: Other
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: C
          Assignee: unassignedclangbugs at nondot.org
          Reporter: tydeman at tybor.com
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

This code shows that the cast operator is not raising the floating point
inexact exception (perhaps because the cast was done at translation time).  I
am using as many options as I can find to get IEEE-754 and C standard
conformance.  This is on ARM CPU.

/*
 * Missing inexact FP exception on cast.
 */

#include <float.h>
#include <fenv.h>
#include <stdio.h>

int main(void){
  int ex;

  feclearexcept( FE_ALL_EXCEPT );
  if( 0.1F == (float)0.1 ){     /* inexact on cast */
    (void)printf("equal\n");
  }else{
    (void)printf("not equal\n");
  }
  ex = fetestexcept( FE_ALL_EXCEPT );
  if( FE_INEXACT != ex ){
    (void)printf("bug: ex = %#x, FE_INEXACT=%#x\n", ex, FE_INEXACT);
  }
  (void)printf("FLT_EVAL_METHOD=%i\n", FLT_EVAL_METHOD);

  return 0;
}

# flags for compiler
export CFLAGS="-H -std=c2x -pedantic -pedantic-errors -O0 -m64 -march=armv8-a
-mcpu=cortex-a72 \
 -ffp-model=strict \
 -ffp-exception-behavior=strict \
 -fhonor-infinities \
 -fhonor-nans \
 -fmath-errno \
 -fno-associative-math \
 -fno-builtin \
 -fno-finite-math-only \
 -fno-reciprocal-math \
 -fno-unsafe-math-optimizations \
 -frounding-math \
 -fsigned-zeros \
 -fstrict-float-cast-overflow \
 -ftrapping-math \
 -Xclang -disable-llvm-optzns \
 ${INCS}"

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