http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48681
Summary: static assertion using DBL_MIN/DBL_MAX/DBL_EPSILON
doesn't work with g++-4.5
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: ste...@space.twc.de
We're using static assertions (assertions that are checked at compile time) to
validate certain properties for DBL_MIN/DBL_MAX/DBL_EPSILON in BEAST. I've
isolated the code and made a standalone example. With g++-4.4, everything
compiles fine, with g++-4.5, it doesn't compile any more. The code is:
/* sassert.cc */
#include "values.h"
#define BIRNET_CPP_PASTE2i(a,b) a ## b /* twofold
indirection is required to expand macros like __LINE__ */
#define BIRNET_CPP_PASTE2(a,b) BIRNET_CPP_PASTE2i (a,b)
#define BIRNET_STATIC_ASSERT_NAMED(expr,asname) typedef struct { char
asname[(expr) ? 1 : -1]; } BIRNET_CPP_PASTE2 (Birnet_StaticAssertion_LINE,
__LINE__)
#define BIRNET_STATIC_ASSERT(expr) BIRNET_STATIC_ASSERT_NAMED
(expr, compile_time_assertion_failed)
BIRNET_STATIC_ASSERT (FLT_MIN <= 1E-37);
BIRNET_STATIC_ASSERT (FLT_MAX >= 1E+37);
BIRNET_STATIC_ASSERT (FLT_EPSILON <= 1E-5);
BIRNET_STATIC_ASSERT (DBL_MIN <= 1E-37);
BIRNET_STATIC_ASSERT (DBL_MAX >= 1E+37);
BIRNET_STATIC_ASSERT (DBL_EPSILON <= 1E-9);
int
main()
{
return 0;
}
# g++-4.4 sassert.cc
works
# g++-4.5 sassert.cc
sassert.cc:11:1: error: array bound is not an integer constant before ']' token
sassert.cc:12:1: error: array bound is not an integer constant before ']' token
sassert.cc:13:1: error: array bound is not an integer constant before ']' token
Preprocessed code for g++-4.4:
==============================
/* [...] */
typedef struct { char compile_time_assertion_failed[(1.17549435e-38F <= 1E-37)
? 1 : -1]; } Birnet_StaticAssertion_LINE8;
typedef struct { char compile_time_assertion_failed[(3.40282347e+38F >= 1E+37)
? 1 : -1]; } Birnet_StaticAssertion_LINE9;
typedef struct { char compile_time_assertion_failed[(1.19209290e-7F <= 1E-5) ?
1 : -1]; } Birnet_StaticAssertion_LINE10;
typedef struct { char compile_time_assertion_failed[(2.2250738585072014e-308 <=
1E-37) ? 1 : -1]; } Birnet_StaticAssertion_LINE11;
typedef struct { char compile_time_assertion_failed[(1.7976931348623157e+308 >=
1E+37) ? 1 : -1]; } Birnet_StaticAssertion_LINE12;
typedef struct { char compile_time_assertion_failed[(2.2204460492503131e-16 <=
1E-9) ? 1 : -1]; } Birnet_StaticAssertion_LINE13;
int
main()
{
return 0;
}
Preprocessed code for g++-4.5:
==============================
typedef struct { char
compile_time_assertion_failed[(1.17549435082228750797e-38F <= 1E-37) ? 1 : -1];
} Birnet_StaticAssertion_LINE8;
typedef struct { char
compile_time_assertion_failed[(3.40282346638528859812e+38F >= 1E+37) ? 1 : -1];
} Birnet_StaticAssertion_LINE9;
typedef struct { char compile_time_assertion_failed[(1.19209289550781250000e-7F
<= 1E-5) ? 1 : -1]; } Birnet_StaticAssertion_LINE10;
typedef struct { char
compile_time_assertion_failed[(((double)2.22507385850720138309e-308L) <= 1E-37)
? 1 : -1]; } Birnet_StaticAssertion_LINE11;
typedef struct { char
compile_time_assertion_failed[(((double)1.79769313486231570815e+308L) >= 1E+37)
? 1 : -1]; } Birnet_StaticAssertion_LINE12;
typedef struct { char
compile_time_assertion_failed[(((double)2.22044604925031308085e-16L) <= 1E-9) ?
1 : -1]; } Birnet_StaticAssertion_LINE13;
int
main()
{
return 0;
}
I'm not sure if this is to be considered a compiler bug (so it should be fixed
in g++), or if the code in question is not valid C++ and should not be used (so
it should be fixed in the application).
