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I'm trying to build readline 6.3 for cygwin (in preparation for bash 4.3), but ran into a snag. Readline tries to redefine 'setjmp' in terms of 'sigsetjmp' via a wrapper header (presumably faster to wrap the problem away than auditing lots of old code to find where setjmp was used?), which works on Linux but fails miserably on Cygwin: ... #if defined (HAVE_POSIX_SIGSETJMP) # define procenv_t sigjmp_buf # if !defined (__OPENNT) # undef setjmp # define setjmp(x) sigsetjmp((x), 1) ... $ printf '#include "config.h" #include <setjmp.h> #include "posixjmp.h" sigsetjmp(a,0)\n' | gcc -E - | tail -n1 __extension__ ({ sigjump_buf *_sjbuf = &(a); ((*_sjbuf)[(13 * 4)] = 0, pthread_sigmask (0, 0, (sigset_t *)((*_sjbuf) + ((13 * 4)+1))), sigsetjmp (*_sjbuf)); }) Basically, because readline's causes two macros to be defined in terms of each other, the expansion of sigsetjmp is trying to invoke a function named sigsetjmp, but no such function exists on Cygwin, leading to this compilation failure: readline.c: In function 'readline_internal_char': readline.c:541:7: error: implicit declaration of function 'sigsetjmp' [-Werror=implicit-function-declaration] Reading POSIX, I see that Cygwin is compliant, and readline is at fault. http://pubs.opengroup.org/onlinepubs/9699919799/functions/setjmp.html is clear: "It is unspecified whether setjmp() is a macro or a function. If a macro definition is suppressed in order to access an actual function, or a program defines an external identifier with the name setjmp, the behavior is undefined." But as the redefine works in Linux, I'm wondering if we tweak things in Cygwin and/or newlib to allow it to work here too. Maybe by making an entry point __setjmp() as an alias for setjmp(), and defining sigsetjmp() in terms of __setjmp(), so that when someone adds a #define wrapper for setjmp, it is no longer a mutually recursive macro naming scenario. In the meantime, I'm resorting to patching up readline code to quit trying to (re)define setjmp. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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