math.h float_t and double_t not typedef'ed when FLT_EVAL_METHOD defined
Jordy Potman
jordy.potman.recore@gmail.com
Sat Nov 17 05:33:00 GMT 2012
Hi,
I am using Newlib with a clang based compiler for our architecture.
I think I have found an issue in Newlib's math.h.
Newlib's math.h does not typedef float_t and double_t when
FLT_EVAL_METHOD is defined.
math.h lines 143-147:
143: #ifndef FLT_EVAL_METHOD
144: #define FLT_EVAL_METHOD 0
145: typedef float float_t;
146: typedef double double_t;
147: #endif /* FLT_EVAL_METHOD */
Clang's float.h defines FLT_EVAL_METHOD (I think gcc's float.h does as
well), which I think is correct according to section 5.2.4.2.2 paragraph
8 of the C99 standard.
Newlib's math.h defines the log2f function as a macro which uses
float_t.
math.h lines 354-357:
354: extern float log2f _PARAMS((float));
355: #if !defined(__cplusplus)
356: #define log2f(x) (logf (x) / (float_t) _M_LN2)
357: #endif
This causes a compilation error if a program includes float.h before
math.h and uses the log2f function:
$ cat log2f_test.c
#include <float.h>
#include <math.h>
float f(float a) {
return log2f(a);
}
$ xentium-clang -std=c99 -c log2f_test.c
log2f_test.c:5:10: error: use of undeclared identifier 'float_t'; did
you mean 'float'?
return log2f(a);
^
/home/potman/opt/xentium-tools-1.0.beta9-linux64/bin/../sysroots/default/include/math.h:359:31: note: expanded from
macro 'log2f'
#define log2f(x) (logf (x) / (float_t) _M_LN2)
^
1 error generated.
I have changed math.h lines 354-357 to the following in our
implementation:
#ifndef FLT_EVAL_METHOD
#define FLT_EVAL_METHOD 0
#endif /* FLT_EVAL_METHOD */
#if FLT_EVAL_METHOD == 1
typedef double float_t;
typedef double double_t;
#elif FLT_EVAL_METHOD == 2
typedef long double float_t;
typedef long double double_t;
#else
typedef float float_t;
typedef double double_t;
#endif
This is my interpretation of how float_t and double_t should be
typedef'ed depending on the value of FLT_EVAL_METHOD as is described in
section 7.12 paragraph 2 of the C99 standard. However I am not a C99
standard expert.
Jordy
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