bad line in /usr/include/math.h
Issac Trotts
trotts@MIT.EDU
Thu Jul 20 19:14:00 GMT 2000
I got a very cryptic error message while compiling a C++ class library
called GiNaC ( http://www.ginac.de/ ) that overloads the function log2
because of the following sinister line in /usr/include/math.h:
#define log2(x) (log(x) / M_LOG2_E)
I first tried to replace the line with inline versions of log2 for float
and double but
the compiler complained that log2 was being redefined. So I changed the line
to
#ifdef __cplusplus
// Do not define log2
#else
#define log2(x) (log(x) / M_LOG2_E)
#endif
and now the code compiles. Btw, I also put the following code:
#ifdef log2
#undef log2
#endif
above the line
unsigned log2(unsigned n);
in the GiNaC header file that originally had the problem, just in case
I get another infected math.h file later on.
-Issac
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