Corinna Vinschen via Cygwin wrote:
On Jan 22 16:47, Christian Franke via Cygwin wrote:
Busybox does not build OOTB on Cygwin due to the addition of itoa/utoa() to
newlib in 2014:
https://cygwin.com/git/?p=newlib-cygwin.git;a=commit;h=32c96dd
This is because Busybox use local functions with same name but different
signature. This does not affect build on FreeBSD, Linux (glibc, musl libc),
... because these functions simply do not exits there. For the busybox
Cygwin package, I use an ugly local hack to fix this.
itoa() is mentioned as a non-standard extension here:
https://en.wikibooks.org/wiki/C_Programming/stdlib.h/itoa
https://cplusplus.com/reference/cstdlib/itoa/
MSVC provides itoa() as a "POSIX version" of _itoa():
https://learn.microsoft.com/cpp/c-runtime-library/reference/itoa-itow
But SUS-1997... POSIX-2018 do not mention these functions:
https://pubs.opengroup.org/onlinepubs/7908799/
https://pubs.opengroup.org/onlinepubs/9699919799/
Newlib guards the prototypes with __MISC_VISIBLE in stdlib.h and
sys/features.h says:
* __MISC_VISIBLE
* Extensions found in both BSD and SVr4 (shorthand for
* (__BSD_VISIBLE || __SVID_VISIBLE)), or newlib-specific
* extensions; enabled by default.
__MISC_VISIBLE is set if and only if _DEFAULT_SOURCE is set, so the comment
below should also include "... or newlib-specific extensions":
* _DEFAULT_SOURCE (or none of the above)
* POSIX-1.2008 with BSD and SVr4 extensions
The above is not suitable to disable only the non-standard functions for
such use cases. Using -D_GNU_SOURCE should IMO not enable functions
unavailable on Linux. This is not the case because _GNU_SOURCE implies
_DEFAULT_SOURCE.
No patch provided for now, as I'm not yet sure how to handle this. Possibly:
- Use __MISC_VISIBLE only for (__BSD_VISIBLE || __SVID_VISIBLE) - under the
assumption that this is applicable for most cases.
- Introduce __NONSTD_VISIBLE for non-standard functions like itoa().
- Introduce _NONSTD_SOURCE to set __NONSTD_VISIBLE independent from other
_*_SOURCE defines.
Counter proposal:
First of all, Cygwin does NOT export itoa/utoa! Only the prototypes
exist from the Cygwin POV.
Thanks, I missed that.
As Cygwin is usually the only newlib project with backward compat
issues, we have two simple choices:
- Drop itoa/utoa entirely, or
- just guard them with
#if __MISC_VISIBLE && !defined (__CYGWIN__)
You can make a proposal like that on the newlib list and then we can
discuss it there, ok?
Done.
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