I think I have found a problem in the g++ header files concerning large file
support. I have seen it on two different AIX machines, one running AIX 5.3
and using gcc 4.1.2, the other running AIX 5.2 and using a slightly later
version of gcc, namely 4.2.2.
cstdio carefully #undefs all the routines in stdio.h and then issues a
"using" directive for each. The problem is that when large file support is
enabled, routines like fgetpos() have been remapped to the 64-bit
equivalents, fgetpos64() in this example.
>From stdio.h:
#ifdef _LARGE_FILES
#define fgetpos fgetpos64
#endif
#ifdef _LARGE_FILE_API
extern int fgetpos64(FILE *, fpos64_t *);
#endif
Then cstdio does
#undef fgetpos
and later ...
using ::fgetpos;
which yields a compilation error because there is no such routine.
The following source code illustrates the problem.
testio.cpp
==========
#include <cstdio>
int main(int argc, char *argv[])
{
FILE
*ff;
ff = fopen("grober.nix", "w");
if (ff == 0)
{
puts("File open failed");
}
else
{
fprintf(ff, "To a %s, happiness is a warm %s\n",
"maggot", "cowpat");
fclose(ff);
}
return 0;
}
When compiled with:
g++ testio.cpp
no error is elicited and the program (a.out) does what is expected.
Compiling with
g++ -D_LARGE_FILES testio.cpp
yields
In file included from testio.cpp:1:
/opt/freeware/lib/gcc/powerpc-ibm-aix5.2.0.0/4.2.2/include/c++/cstdio:109:
error: '::fgetpos' has not been declared
/opt/freeware/lib/gcc/powerpc-ibm-aix5.2.0.0/4.2.2/include/c++/cstdio:111:
error: '::fopen' has not been declared
/opt/freeware/lib/gcc/powerpc-ibm-aix5.2.0.0/4.2.2/include/c++/cstdio:116:
error: '::freopen' has not been declared
/opt/freeware/lib/gcc/powerpc-ibm-aix5.2.0.0/4.2.2/include/c++/cstdio:119:
error: '::fsetpos' has not been declared
testio.cpp: In function 'int main(int, char**)':
testio.cpp:8: error: 'fopen' was not declared in this scope
All the routines listed in the error messages are subject to the 64-bit
remapping done by stdio.h and broken by cstdio.
Now I tried the same thing on some other platforms, namely
HPUX ia64 g++ 4.2.2
HPUX parisc g++ 4.2.2
Linux x86_64 g++ 3.4.5
Linux x86 g++ 3.4.6
and none of those exhibited the problem described above. I confess that I
do not know why, and it suggests that either my analysis is flawed or the
large file support is not being used by C++ programs on those platforms.
(I noted that _LARGE_FILES and _LARGE_FILE_API are disjoint but I did not
spend any time trying to figure out why.)
