libast: cleanup: remove obsolete pre-sigaction(2) fallbacks

Like the similar operation for ksh in 3e2e519, this cleans up a
bunch of dead code in libast and the associated feature tests. The
feature tests for sigaction(2) and friends are also removed; their
presence is now assumed (POSIX specified them in 1988).

Notable changes:

src/lib/libast/comp/sigunblock.c,
src/lib/libast/features/map.c:
- Always use the AST version of sigunblock(3), never the native
  version (if any), and rename it to _ast_sigunblock via map.c just
  to be sure a native version won't override it. There is no
  guarantee native versions are the same. For instance, on QNX,
  sigunblock() takes a signal mask argument, not a signal number.

src/lib/libast/Mamfile

@@ -4521,7 +4521,7 @@ make install virtual
 	done
 
 	note * section 3 manual pages
-	loop SECT3MAN LIBAST aso ast cdt chr compat error find fmt fmtls ftwalk getcwd hash iblocks int ip6 magic mem mime modecanon optget path proc re regex setenviron sfio sig spawnveg stk strcopy strdup strelapsed strerror stresc streval strgid strmatch stropt strperm strsignal strsort strtape strton struid swap tab tm tmx tok touch tv
+	loop SECT3MAN LIBAST aso ast cdt chr compat error find fmt fmtls ftwalk getcwd hash iblocks int ip6 magic mem mime modecanon optget path proc re regex setenviron sfio sig spawnveg stk strcopy strdup strelapsed strerror stresc streval strgid strmatch stropt strperm strsort strtape strton struid swap tab tm tmx tok touch tv
 		make %{INSTALLROOT}/man/man3/%{SECT3MAN}.3
 			makp man/%{SECT3MAN}.3
 			exec - cp -f %{<} %{@}

src/lib/libast/comp/sigflag.c

@@ -2,7 +2,7 @@
 *                                                                      *
 *               This software is part of the ast package               *
 *          Copyright (c) 1985-2011 AT&T Intellectual Property          *
-*          Copyright (c) 2020-2023 Contributors to ksh 93u+m           *
+*          Copyright (c) 2020-2024 Contributors to ksh 93u+m           *
 *                      and is licensed under the                       *
 *                 Eclipse Public License, Version 2.0                  *
 *                                                                      *
@@ -30,7 +30,6 @@ NoN(sigflag)
 int
 sigflag(int sig, int flags, int set)
 {
-#if _lib_sigaction
 	struct sigaction	sa;
 
 	if (sigaction(sig, NULL, &sa))
@@ -40,9 +39,6 @@ sigflag(int sig, int flags, int set)
 	else
 		sa.sa_flags &= ~flags;
 	return sigaction(sig, &sa, NULL);
-#else
-	return -1;
-#endif
 }
 
 #endif

src/lib/libast/comp/sigunblock.c

@@ -2,7 +2,7 @@
 *                                                                      *
 *               This software is part of the ast package               *
 *          Copyright (c) 1985-2011 AT&T Intellectual Property          *
-*          Copyright (c) 2020-2023 Contributors to ksh 93u+m           *
+*          Copyright (c) 2020-2024 Contributors to ksh 93u+m           *
 *                      and is licensed under the                       *
 *                 Eclipse Public License, Version 2.0                  *
 *                                                                      *
@@ -17,24 +17,24 @@
 *                                                                      *
 ***********************************************************************/
 
-#include <ast.h>
-
-#if _lib_sigunblock
-
-NoN(sigunblock)
-
-#else
+/*
+ * There is no longer a test for a native sigunblock() here because we
+ * always use the sigprocmask(3) version now. Obsolete functions don't
+ * necessarily mix with the POSIX interface. Plus, on QNX, sigunblock()
+ * expects a signal mask argument, not a signal number.
+ */
 
+#include <ast.h>
 #include <sig.h>
 
-#ifndef SIG_UNBLOCK
-#undef	_lib_sigprocmask
-#endif
+/*
+ * remove s from the set of blocked signals
+ * s==0 unblocks them all
+ */
 
 int
 sigunblock(int s)
 {
-#if _lib_sigprocmask
 	int		op;
 	sigset_t	mask;
 
@@ -46,14 +46,4 @@ sigunblock(int s)
 	}
 	else op = SIG_SETMASK;
 	return sigprocmask(op, &mask, NULL);
-#else
-#if _lib_sigsetmask
-	return sigsetmask(s ? (sigsetmask(0L) & ~sigmask(s)) : 0L);
-#else
-	NoP(s);
-	return 0;
-#endif
-#endif
 }
-
-#endif

src/lib/libast/features/lib

@@ -33,8 +33,8 @@ lib	mbtowc,mbrtowc,memalign,memdup
 lib	mkdir,mkfifo,mktemp,mktime
 lib	mount,opendir,pathconf
 lib	readlink,remove,rename,rewinddir,rmdir,setlocale
-lib	setpgrp,setpgrp2,setreuid,setuid,sigaction
-lib	sigprocmask,sigsetmask,sigunblock,sigvec,socketpair
+lib	setpgrp,setpgrp2,setreuid,setuid
+lib	socketpair
 lib	spawn,spawnve
 lib	strcoll,strdup,strerror,strcasecmp,strncasecmp,strlcat,strlcpy
 lib	strmode,strxfrm,strftime,swab,symlink,sysconf,sysinfo
@@ -376,12 +376,6 @@ std	remove note{ stuck with standard remove() }end nostatic{
 	int main(void) { return unlink("foo"); }
 }end
 
-std	signal note{ stuck with standard signal }end nolink{
-	extern void abort(void);
-	int signal(void) { return 0; }
-	int main(void) { signal(); abort(); return 0; }
-}end
-
 std	strcoll note{ standard strcoll works }end execute{
 	#include <string.h>
 	#define S	"hello world"

src/lib/libast/features/map.c

@@ -103,11 +103,12 @@ main(void)
 	printf("#define glob		_ast_glob\n");
 	printf("#undef	globfree\n");
 	printf("#define globfree	_ast_globfree\n");
-#if _map_libc || (!_std_signal && (_lib_sigaction && defined(SA_NOCLDSTOP) || _lib_sigvec && defined(SV_INTERRUPT)))
-	/* use the libast signal() function (aka sigaction) when applicable */
+	/* always rename AST signal(3) to _ast_signal; this avoids breakage when using ASan */
 	printf("#undef	signal\n");
 	printf("#define signal      	_ast_signal\n");
-#endif
+	/* do the same with sigunblock(), just to be sure (e.g., native QNX sigunblock() is different) */
+	printf("#undef	sigunblock\n");
+	printf("#define sigunblock      _ast_sigunblock\n");
 #if _map_libc
 	printf("#undef	memdup\n");
 	printf("#define memdup		_ast_memdup\n");
@@ -263,8 +264,6 @@ main(void)
 	printf("#define setenviron      _ast_setenviron\n");
 	printf("#undef	sigcritical\n");
 	printf("#define sigcritical      _ast_sigcritical\n");
-	printf("#undef	sigunblock\n");
-	printf("#define sigunblock      _ast_sigunblock\n");
 	printf("#undef	stracmp\n");
 	printf("#define stracmp		_ast_stracmp\n");
 	printf("#undef	strcopy\n");

src/lib/libast/misc/procclose.c

@@ -67,14 +67,7 @@ procclose(Proc_t* p)
 					signal(SIGINT, p->sigint);
 				if (p->sigquit != SIG_IGN)
 					signal(SIGQUIT, p->sigquit);
-#if _lib_sigprocmask
 				sigprocmask(SIG_SETMASK, &p->mask, NULL);
-#elif _lib_sigsetmask
-				sigsetmask(p->mask);
-#else
-				if (p->sigchld != SIG_DFL)
-					signal(SIGCHLD, p->sigchld);
-#endif
 			}
 			status = status == -1 ?
 				 EXIT_QUIT :

src/lib/libast/misc/proclib.h

@@ -31,19 +31,12 @@
 #include <sig.h>
 #include <wait.h>
 
-#if _lib_sigprocmask
-typedef sigset_t Sig_mask_t;
-#else
-typedef unsigned long Sig_mask_t;
-#endif
-
 struct Mods_s;
 
 #define _PROC_PRIVATE_ \
 	struct Mod_s*	mods;		/* process modification state	*/ \
 	long		flags;		/* original PROC_* flags	*/ \
-	Sig_mask_t	mask;		/* original blocked sig mask	*/ \
-	Sig_handler_t	sigchld;	/* PROC_FOREGROUND SIG_DFL	*/ \
+	sigset_t	mask;		/* original blocked sig mask	*/ \
 	Sig_handler_t	sigint;		/* PROC_FOREGROUND SIG_IGN	*/ \
 	Sig_handler_t	sigquit;	/* PROC_FOREGROUND SIG_IGN	*/
 

src/lib/libast/misc/procopen.c

@@ -407,9 +407,7 @@ procopen(const char* cmd, char** argv, char** envv, long* modv, int flags)
 #if !_pipe_rw && !_lib_socketpair
 	int		poi[2];
 #endif /* !_pipe_rw && !_lib_socketpair */
-#if _lib_sigprocmask || _lib_sigsetmask
-	Sig_mask_t	mask;
-#endif /* _lib_sigprocmask || _lib_sigsetmask */
+	sigset_t	mask;
 #if _use_spawnveg
 	int		newenv = 0;
 #endif /* _use_spawnveg */
@@ -498,16 +496,9 @@ procopen(const char* cmd, char** argv, char** envv, long* modv, int flags)
 			signalled = 1;
 			proc->sigint = signal(SIGINT, SIG_IGN);
 			proc->sigquit = signal(SIGQUIT, SIG_IGN);
-#if _lib_sigprocmask
 			sigemptyset(&mask);
 			sigaddset(&mask, SIGCHLD);
 			sigprocmask(SIG_BLOCK, &mask, &proc->mask);
-#elif _lib_sigsetmask
-			mask = sigmask(SIGCHLD);
-			proc->mask = sigblock(mask);
-#else
-			proc->sigchld = signal(SIGCHLD, SIG_DFL);
-#endif /* _lib_sigprocmask */
 		}
 		if ((flags & PROC_ORPHAN) && pipe(pop))
 			goto bad;
@@ -526,14 +517,7 @@ procopen(const char* cmd, char** argv, char** envv, long* modv, int flags)
 				proc->sigquit = SIG_DFL;
 				signal(SIGQUIT, proc->sigquit);
 			}
-#if _lib_sigprocmask
 			sigprocmask(SIG_SETMASK, &proc->mask, NULL);
-#elif _lib_sigsetmask
-			sigsetmask(proc->mask);
-#else
-			if (proc->sigchld != SIG_IGN)
-				signal(SIGCHLD, SIG_DFL);
-#endif /* _lib_sigprocmask */
 		}
 		else if (proc->pid == -1)
 			goto bad;
@@ -760,16 +744,9 @@ procopen(const char* cmd, char** argv, char** envv, long* modv, int flags)
 				signalled = 1;
 				proc->sigint = signal(SIGINT, SIG_IGN);
 				proc->sigquit = signal(SIGQUIT, SIG_IGN);
-#if _lib_sigprocmask
 				sigemptyset(&mask);
 				sigaddset(&mask, SIGCHLD);
 				sigprocmask(SIG_BLOCK, &mask, &proc->mask);
-#elif _lib_sigsetmask
-				mask = sigmask(SIGCHLD);
-				proc->mask = sigblock(mask);
-#else
-				proc->sigchld = signal(SIGCHLD, SIG_DFL);
-#endif /* _lib_sigprocmask */
 			}
 		}
 		else if (modv)
@@ -843,14 +820,7 @@ procopen(const char* cmd, char** argv, char** envv, long* modv, int flags)
 			signal(SIGINT, proc->sigint);
 		if (proc->sigquit != SIG_IGN)
 			signal(SIGQUIT, proc->sigquit);
-#if _lib_sigprocmask
 		sigprocmask(SIG_SETMASK, &proc->mask, NULL);
-#elif _lib_sigsetmask
-		sigsetmask(proc->mask);
-#else
-		if (proc->sigchld != SIG_DFL)
-			signal(SIGCHLD, proc->sigchld);
-#endif /* _lib_sigprocmask */
 	}
 	if ((flags & PROC_CLEANUP) && modv)
 		for (i = 0; n = modv[i]; i++)