On Tue, 31 Jan 2012, Jyun-Yan You wrote:
Description:
ucontext.h does not include any header file that defines size_t.
If we write a program that includes sys/ucontext.h, it may cause compilation
errors.
ports/164654 is the real case.
-current added 2 new prototypes with 5 bugs altogether; 3 style bugs and
2 namespace bugs:
- 2 indentation errors. Old prototypes use normal indentation.
- 1 named parameter. Old prototypes don't use named parameters.
- the name of the parameter pollutes the application namespace
- size_t is used, but is not defined. Elsewhere (for stack_t),
size_t is avoided by using __size_t for stack_t, but there is
gross namespace pollution from including <sys/signal.h> for
nothing more than stack_t.
--- ucontext.h.diff begins here ---
--- sys/sys/ucontext.h.orig 2012-01-31 12:50:57.702804441 +0800
+++ sys/sys/ucontext.h 2012-01-31 12:51:26.217639882 +0800
@@ -69,6 +69,11 @@
#ifndef _KERNEL
+#ifndef _SIZE_T_DECLARED
+typedef __size_t size_t;
+#define _SIZE_T_DECLARED
+#endif
+
__BEGIN_DECLS
int getcontext(ucontext_t *);
--- ucontext.h.diff ends here ---
size_t is only used (for 1 of the new prototypes) if __BSD_VISIBLE.
That prototype's function is named with 2 underscores, so it is not
usable by applications, so the prototype might as well use 2 underscores
to hide __size_t too. Otherwise, the above ifdef should be conditional
on __BSD_VISIBLE too.
Here is an old patch to reduce and document some pollution, and to fix
some style bugs.
% Index: ucontext.h
% ===================================================================
% RCS file: /home/ncvs/src/sys/sys/ucontext.h,v
% retrieving revision 1.11
% diff -u -2 -r1.11 ucontext.h
% --- ucontext.h 9 Nov 2003 20:31:04 -0000 1.11
% +++ ucontext.h 10 Nov 2003 09:38:33 -0000
% @@ -32,5 +32,11 @@
% #define _SYS_UCONTEXT_H_
%
% +#ifdef _KERNEL
% +#include <sys/_sigset.h>
% +#else
% +/* XXX need stack_t as well as sigset_t. */
% #include <sys/signal.h>
% +#endif
% +
% #include <machine/ucontext.h>
%
% @@ -50,6 +56,7 @@
% stack_t uc_stack;
% int uc_flags;
% +/* XXX namespace pollution. */
% #define UCF_SWAPPED 0x00000001 /* Used by swapcontext(3). */
% - int __spare__[4];
% + int uc_spare[4];
% } ucontext_t;
%
% @@ -61,27 +68,22 @@
% struct ucontext4 *uc_link;
% stack_t uc_stack;
% - int __spare__[8];
% + int uc_spare[8];
% };
% -#else /* __i386__ || __alpha__ */
% +#else /* __i386__ || __alpha__ */
% #define ucontext4 ucontext
% -#endif /* __i386__ || __alpha__ */
% -#endif /* _KERNEL */
% +#endif /* __i386__ || __alpha__ */
% +#endif /* _KERNEL */
%
% #ifndef _KERNEL
% -
% __BEGIN_DECLS
% -
% int getcontext(ucontext_t *);
% -int setcontext(const ucontext_t *);
% void makecontext(ucontext_t *, void (*)(void), int, ...);
% -int signalcontext(ucontext_t *, int, __sighandler_t *);
% +int setcontext(const ucontext_t *);
% +int signalcontext(ucontext_t *, int, void (*)(int));
% int swapcontext(ucontext_t *, const ucontext_t *);
% -
% __END_DECLS
%
% #else /* _KERNEL */
%
% -struct thread;
% -
% /*
% * Flags for get_mcontext(). The low order 4 bits (i.e a mask of 0x0f) are
% @@ -91,8 +93,8 @@
% #define GET_MC_CLEAR_RET 1
%
% -/* Machine-dependent functions: */
% +struct thread;
% +
% int get_mcontext(struct thread *, mcontext_t *, int);
% int set_mcontext(struct thread *, const mcontext_t *);
% -
% #endif /* !_KERNEL */
%
Further investigation shows that size_t should be declared unconditionally
anyway, for stack_t in both signal.h and ucontext.h. POSIX reqires
"stack_t uc_stack" in ucontext_t (this bogusly also requires ucontext_t
to be highly non-opaque, and in fact a struct with certain members),
and it requires stack_t to be as in signal.h. And it requires "size_t
ss_size" in stack_t (this bogusly also requires stack_t to be highly
non-opaque, and in fact a struct with certain members). stack_t and
ucontext.h are XSI extensions, so their namespace errors are not
The history of this is not completely clear, but some of it is:
- in POSIX.1-2001, stack_t and ucontext.h were only XSI extensions.
XSI even required signal.h to declare ucontext_t! FreeBSD never
implemented the latter.
- in POSIX-1.2007-draft, ucontext.h no longer exists. stack_t and
ucontext_t are now non-optional (C extensions instead of an XSI
extensions), and are required to be implemented in signal.h. FreeBSD
doesn't seem to have caught up with this. stack_t is still only used
by sigaltstack(), which is still only an XSI extension. But to go
with this pollution, size_t is now explicitly required to be declared
in signal.h. So FreeBSD's careful avoidance of this pollution is now
non-conforming :-(. FreeBSD clearly hasn't caught up with this. It
still declares stack_t in signal.h conditionally on __XSI_VISIBLE
(which is the default). sigaltstack() and struct sigalstack are
standard in BSD, but the stack_t mistake isn't.
Bruce
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