Test case:
#include <math.h>
int isnan_wrapper(double value) { return isnan(value); }
Output:
$ g++ -Wconversion -c snippet.cpp
warning: conversion to 'float' from 'double' may alter its value
warning: conversion to 'int' from 'double' may alter its value
First warning is caused by the fact in C++ mode is __mingw_choose_expr
using ternary operator and warning is triggered also case which is not
called.
Second warning is caused by the fact that type of expression
(__builtin_trap(),x) for isnan(x) is double, but return value of
isnan_wrapper() is int. But this expression never returns.
Fix the first problem to use explicit cast for __isnan* calls which
correspondents to matched __mingw_types_compatible_p types.
And fix second problem by changing expression to something which has type
of int.
Bug: https://sourceforge.net/p/mingw-w64/bugs/481/
---
mingw-w64-headers/crt/math.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/mingw-w64-headers/crt/math.h b/mingw-w64-headers/crt/math.h
index cacdd4753366..5cc24a20609e 100644
--- a/mingw-w64-headers/crt/math.h
+++ b/mingw-w64-headers/crt/math.h
@@ -594,14 +594,14 @@ __mingw_choose_expr (
\
#define isnan(x) \
__mingw_choose_expr ( \
__mingw_types_compatible_p (__typeof__ (x), double), \
- __isnan(x), \
+ __isnan((double)(x)), \
__mingw_choose_expr ( \
__mingw_types_compatible_p (__typeof__ (x), float), \
- __isnanf(x), \
+ __isnanf((float)(x)), \
__mingw_choose_expr ( \
__mingw_types_compatible_p (__typeof__ (x), long double), \
- __isnanl(x), \
- __dfp_expansion(__isnan,(__builtin_trap(),x),x))))
+ __isnanl((long double)(x)), \
+ __dfp_expansion(__isnan,(__builtin_trap(),(int)0),x))))
/* 7.12.3.5 */
#define isnormal(x) (fpclassify(x) == FP_NORMAL)
--
2.20.1
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