Hi Eric!
On Wed, Apr 30, 2014 at 06:51:23PM -0600, Eric Blake wrote:
> On 04/30/2014 06:12 PM, Thomas Klausner wrote:
> > Hi!
> >
> > I found out that the prototypes for backtrace() and backtrace_symbol()
> > differ on some operating systems.
> >
>
> >
> > The main difference is that on NetBSD, size_t is used for most
> > arguments that are int on the other systems; also,
> > backtrace_symbols_fd returns an int.
> >
> > I'd like to test for the difference int <-> size_t in a configure
> > script so I can get integer type/sign conversion-warnings free code on
> > all these operating systems.
> >
> > I'm however not sure how to do this. Does anyone have a suggestion?
>
> Yep - use function pointer assignment or redeclaration to force the
> compiler to complain if the redeclaration used the wrong type. Gnulib
> has some examples; here's one with ioctl(), which on Linux takes an
> 'unsigned long' instead of the POSIX 'int' for the second parameter:
Thanks for the idea and the examples!
Here's what I came up with:
AC_CACHE_CHECK([parameter type for backtrace()],
[am_cv_proto_backtrace_type],
[AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
[[
#include <execinfo.h>
extern
#ifdef __cplusplus
"C"
#endif
size_t backtrace(void **addrlist, size_t len);
]])
],
[am_cv_proto_backtrace_type=size_t],
[am_cv_proto_backtrace_type=int])
])
AC_DEFINE_UNQUOTED([backtrace_t], [$am_cv_proto_backtrace_type],
[Define to return type for backtrace().])
It seems to work fine on NetBSD, OS X, and Linux.
This way I can define my variables
backtrace_t len;
and it'll work even if I don't have any backtrace() functionality.
Cheers,
Thomas
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