Fix compile when using tcc >0.9.27 (#238)

This allows ksh to be compiled with versions of tcc that define
__dso_handle in libtcc1.a, i.e., versions as of this commit:
https://repo.or.cz/tinycc.git/commit/dd60b20c

Older versions of tcc still fail to compile ksh, although now they
fail after reaching the libdll feature test. I'm not sure if fixing
that is feasible since even if I hack out the failing libdll
feature test, ksh fails to link with a '__dso_handle' error.

src/lib/libast/comp/atexit.c,
src/lib/libast/features/lib,
src/lib/libast/vmalloc/vmexit.c:
- From what I've been able to gather the only OSes with support
  for on_exit are Linux and SunOS 4. However, on_exit takes two
  arguments, so the macro that defines it as taking one argument
  is incorrect. Since Solaris (SunOS 5) no longer has this call
  and the macro breaks on Linux, the clean fix is to remove it
  (atexit(3) is used instead).

src/lib/libast/include/ast.h:
- When compiling with tcc on FreeBSD, pretend to be gcc 2.95.3
  instead of gcc 9.3.0. This stops /usr/include/math.h from
  activating gcc 3.0+ math compiler builtins that don't exist on
  tcc, while still identifying as gcc which is needed to avoid
  other FreeBSD system header breakage.

src/cmd/builtin/Mamfile,
src/cmd/builtin/features/pty,
src/lib/libdll/Mamfile,
src/lib/libdll/features/dll:
- tcc forbids combining the -c compiler flag with -l* linker flags.
  Use the -lm flag in the iffe feature tests instead of the
  Mamfiles. This avoids iffe combining -lm with the -c flag.

src/lib/libast/vmalloc/malloc.c:
- Fix failure to compile with -D_std_malloc.
  This patch is from OpenSUSE:
  https://build.opensuse.org/package/view_file/shells/ksh/ksh93-malloc-hook.dif
  As it turns out tcc needs this change to build ksh with
  -D_std_malloc, so it has been applied.

Co-authored-by: Martijn Dekker <martijn@inlv.org>
Resolves: https://github.com/ksh93/ksh/issues/232

src/cmd/builtin/Mamfile

@@ -37,7 +37,7 @@ make install
 					meta FEATURE/pty features/%>FEATURE/% features/pty pty
 					make features/pty
 					done features/pty
-					exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${KSH_RELFLAGS} ${CCFLAGS} ${LDFLAGS} -lm" ref ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libast} ${mam_libcmd} : run features/pty
+					exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${KSH_RELFLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libast} ${mam_libcmd} : run features/pty
 				done FEATURE/pty generated
 				make ${PACKAGE_ast_INCLUDE}/ast_time.h implicit
 				done ${PACKAGE_ast_INCLUDE}/ast_time.h

src/cmd/builtin/features/pty

@@ -13,7 +13,7 @@ lib	openpty,_getpty,ptsname -lutil
 lib	grantpt,unlockpt,posix_openpt stdlib.h
 lib	cfmakeraw termios.h
 
-tst - output{
+tst - -lm output{
 	#include	<fcntl.h>
 	#if _lib_ptsname
 	#include	<stdlib.h>

src/lib/libast/comp/atexit.c

@@ -34,11 +34,7 @@ NoN(atexit)
 
 #else
 
-#if _lib_onexit || _lib_on_exit
-
-#if !_lib_onexit
-#define onexit		on_exit
-#endif
+#if _lib_onexit
 
 extern int		onexit(void(*)(void));
 

src/lib/libast/features/lib

@@ -29,7 +29,7 @@ lib	getopt,getsubopt,getopt_long,getopt_long_only
 lib	glob,index,iswblank,iswctype,killpg,link,localeconv,madvise
 lib	mbtowc,mbrtowc,memalign,memchr,memcpy,memdup,memmove,memset
 lib	mkdir,mkfifo,mktemp,mktime
-lib	mount,on_exit,onexit,opendir,pathconf
+lib	mount,onexit,opendir,pathconf
 lib	readlink,remove,rename,rewinddir,rindex,rmdir,setlocale
 lib	setpgid,setpgrp,setpgrp2,setreuid,setsid,setuid,sigaction
 lib	sigprocmask,sigsetmask,sigunblock,sigvec,socketpair

src/lib/libast/include/ast.h

@@ -78,6 +78,19 @@ struct _sfio_s;
 #endif
 #endif
 
+/*
+ * tcc on FreeBSD: Avoid using nonexistent math
+ * builtins by pretending to be an ancient gcc.
+ */
+#if __TINYC__ && __GNUC__ >= 3 && __FreeBSD__
+#undef __GNUC__
+#undef __GNUC_MINOR__
+#undef __GNUC_PATCHLEVEL__
+#define __GNUC__ 2
+#define __GNUC_MINOR__ 95
+#define __GNUC_PATCHLEVEL__ 3
+#endif
+
 /*
  * exit() support -- this matches shell exit codes
  */

src/lib/libast/vmalloc/malloc.c

@@ -1040,12 +1040,8 @@ extern Void_t*	F1(_ast_valloc, size_t,n) { return valloc(n); }
 
 #if !_UWIN
 
-#if !_malloc_hook
-
 #include	<malloc.h>
 
-#endif
-
 typedef struct mallinfo Mallinfo_t;
 typedef struct mstats Mstats_t;
 

src/lib/libast/vmalloc/vmexit.c

@@ -93,7 +93,7 @@ int	type;
 	return type;
 }
 
-#endif	/* _lib_onexit || _lib_on_exit */
+#endif	/* _lib_onexit */
 
 #endif /*!PACKAGE_ast*/
 

src/lib/libdll/Mamfile

@@ -154,7 +154,7 @@ make install
 							done features/dll
 							bind -ldl dontcare
 							bind -last
-							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${KSH_RELFLAGS} ${CCFLAGS} ${LDFLAGS} -lm" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdl} ${mam_libast} : run features/dll
+							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${KSH_RELFLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdl} ${mam_libast} : run features/dll
 						done FEATURE/dll generated
 						exec - cmp 2>/dev/null -s FEATURE/dll dlldefs.h || { rm -f dlldefs.h; silent test -d . || mkdir .; cp FEATURE/dll dlldefs.h; }
 					done dlldefs.h generated

src/lib/libdll/features/dll

@@ -74,7 +74,7 @@ tst	run{
 	esac
 	echo "#define _DLL_NEXT_PATH	\"$lib\""
 }end
-tst	- output{
+tst	- -lm output{
 	#include <math.h>
 	#if defined(__MVS__) && !defined(__SUSV3)
 	#define __SUSV3		1