[CMake] several questions about cmake

[Mark Roden]

I'm starting to get deep into CMake, and I have a few questions as I
try to convert the socket++ library such that it can be compiled by
CMake on Windows.

1) The default install directory on Windows is C:\Program Files, or
C:\Program Files (x86) on 64 bit.  This default will not work on
Windows 7 (and perhaps Vista), because the user isn't running as
administrator anymore, and only administrators can modify that
directory.  There should probably be a warning to that effect on
windows systems; otherwise, there are painful ways to run install, but
they are painful.

2) I'm trying to check to see if a certain C++ code chunk will
compile.  The line is:

CHECK_CXX_SOURCE_COMPILES("
#include <string.h>
#include <stdio.h>
 void main(){
  char buf[100];
  char buf2[100];
  strncpy(buf2, buf, 5);
  buf2[5] = '\0';
  puts(buf2);
 }" EXTERN_C)

The EXTERN_C test is failing here.  The problem is, I can cut and
paste that code into a blank project in vs2008 and it compiles just
fine.  Is there a way to see the compiler error, or to determine why
that would fail?

The code in the configure.in file is:

AC_TRY_LINK([
# include <string.h>
# include <stdio.h>
], [
  char buf[100];
  strcpy(buf, "Hello world\n");
],
  bz_cv_cplusplus_needexternCwrapper=no,
  bz_cv_cplusplus_needexternCwrapper=yes)
])

I can't use that directly (or can I?) because the quotation marks in
"Hello World" prematurely cut off the code in the SOURCE section of
CHECK_CXX_SOURCE_COMPILES, and I get an error that the variable World"
makes no sense.

3) There is a check for the presence of the Libg++ library, but no
specific mention of which function is needed.  According to what I can
find on CheckLibraryExists, I need to provide a specific function to
determine if that library is present.  The code in configure.in is:

AC_CHECK_HEADER(_G_config.h, AC_DEFINE(_S_LIBGXX))

In that case, should I be looking for a particular function in
_G_config.h (which I don't have, since I'm on Windows) and just using
it arbitrarily?  I'm not even close to the point where this code can
fail in compilation and therefore determine the error directly.

4) There are two checks for potentially predefined variables, namely
sys_siglist and sys_errlist.  The code to check for these looks like:

AC_CACHE_VAL(socketxx_cv_siglist, [
AC_TRY_LINK([
# include <unistd.h>
# include <sys/signal.h>
], [
#ifndef _sys_siglist
  extern char* _sys_siglist[];
#endif
  puts(*_sys_siglist);
],
socketxx_cv_siglist=_sys_siglist,
socketxx_cv_siglist=sys_siglist) ])
AC_DEFINE_UNQUOTED(SYS_SIGLIST, $socketxx_cv_siglist)

Windows doesn't have unistd.h or sys/signal.h, so I know that this
will fail, regardless of the test.  I'm unfamiliar with these
variables; does anyone have any insight into them?  It looks like if
the code compiles, the variable _sys_siglist will be used, otherwise,
sys_siglist, whatever that is.  I'm tempted to just say that it is
what it is, and if other unix users have issues, we can fix the cmake
file then.  The typical sloppiness of someone not dealing with their
native platform, I guess :)

There are other problems with converting this file, but I want to
start with this one and still hack away at the others.

Thanks!
Mark