diff --git a/src/cmd/builtin/Mamfile b/src/cmd/builtin/Mamfile
index 71118b5cd185..67ecd21388ca 100644
--- a/src/cmd/builtin/Mamfile
+++ b/src/cmd/builtin/Mamfile
@@ -112,7 +112,7 @@ make install virtual
 			exec - ${CC} ${mam_cc_FLAGS} ${CCFLAGS} -I. -I${PACKAGE_ast_INCLUDE} -DERROR_CATALOG=\""builtin"\" -DCMD_STANDALONE=b_pty -c pty.c
 		done pty.o
 		bind -lutil dontcare
-		exec - ${CC} ${CCLDFLAGS} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS} ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -o pty pty.o ${mam_libutil} ${mam_libast} -lm ${mam_libcmd}
+		exec - ${CC} ${CCLDFLAGS} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS} ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -o pty pty.o ${mam_libutil} ${mam_libast} ${mam_libcmd}
 	done pty
 	make ${INSTALLROOT}/bin
 		exec - mkdir -p ${INSTALLROOT}/bin
diff --git a/src/cmd/builtin/features/pty b/src/cmd/builtin/features/pty
index a7c20d306325..73a44e4733e7 100644
--- a/src/cmd/builtin/features/pty
+++ b/src/cmd/builtin/features/pty
@@ -11,8 +11,7 @@ lib	openpty,_getpty,ptsname -lutil
 lib	grantpt,unlockpt,posix_openpt stdlib.h
 lib	cfmakeraw termios.h
 
-# try once with -lm, once without
-tst - -lm - - output{
+tst output{
 	#include	<fcntl.h>
 	#if _lib_ptsname
 	#include	<stdlib.h>
@@ -51,11 +50,8 @@ tst - -lm - - output{
 		return 0;
 	}
 }end fail{
-	case ${_features_pty_TRIEDONCE-no} in
-	no)	_features_pty_TRIEDONCE=yes ;;
-	*)	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
-		exit 1 ;;
-	esac
+	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
+	exit 1
 }end
 
 extern	_getpty		char*		(int*, int, mode_t, int)
diff --git a/src/cmd/ksh93/Mamfile b/src/cmd/ksh93/Mamfile
index fe3562f9a5b9..3e4fb7078806 100644
--- a/src/cmd/ksh93/Mamfile
+++ b/src/cmd/ksh93/Mamfile
@@ -23,17 +23,16 @@ make install virtual
 		bind -ldll
 		bind -lcmd
 		bind -last
-		bind -lm dontcare
 		bind -lnsl dontcare
 		make shell.req
 			prev ${INSTALLROOT}/bin/mkreq
-			exec - mkreq ${CC} ${mam_cc_FLAGS} ${CCFLAGS} : ${LDFLAGS} : shell dll cmd ast m jobs i socket nsl secdb network
+			exec - mkreq ${CC} ${mam_cc_FLAGS} ${CCFLAGS} : ${LDFLAGS} : shell dll cmd ast jobs i socket nsl secdb network
 		done shell.req
 		make shopt.h notrace implicit
 			make FEATURE/options implicit
 				prev features/options
 				prev shell.req
-				exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} : run features/options
+				exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/options
 			done FEATURE/options
 			prev SHOPT.sh
 			prev Mamfile
@@ -108,13 +107,13 @@ make install virtual
 			make sh/pmain.c
 				make FEATURE/externs implicit
 					prev features/externs
-					exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} : run features/externs
+					exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/externs
 				done FEATURE/externs
 				make include/shell.h implicit
 					make include/fault.h implicit
 						make FEATURE/sigfeatures implicit
 							prev features/sigfeatures
-							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} : run features/sigfeatures
+							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/sigfeatures
 						done FEATURE/sigfeatures
 						make ${PACKAGE_ast_INCLUDE}/sfio.h implicit
 							prev ${PACKAGE_ast_INCLUDE}/sfio_s.h implicit
@@ -247,7 +246,7 @@ make install virtual
 						prev include/shtable.h
 						make FEATURE/dynamic implicit
 							prev features/dynamic
-							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} : run features/dynamic
+							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/dynamic
 							prev ${PACKAGE_ast_INCLUDE}/dlldefs.h
 						done FEATURE/dynamic
 						prev ${PACKAGE_ast_INCLUDE}/option.h
@@ -307,17 +306,17 @@ make install virtual
 						make include/terminal.h implicit
 							make FEATURE/ttys implicit
 								prev features/ttys
-								exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} : run features/ttys
+								exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/ttys
 							done FEATURE/ttys
 						done include/terminal.h
 						prev ${PACKAGE_ast_INCLUDE}/sig.h
 						make FEATURE/locale implicit
 							prev features/locale
-							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} : run features/locale
+							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/locale
 						done FEATURE/locale
 						make FEATURE/cmds implicit
 							prev features/cmds
-							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} : run features/cmds
+							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/cmds
 						done FEATURE/cmds
 					done include/edit.h
 					prev include/builtins.h
@@ -340,7 +339,7 @@ make install virtual
 					prev ${PACKAGE_ast_INCLUDE}/times.h
 					make FEATURE/time implicit
 						prev features/time
-						exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} : run features/time
+						exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/time
 						make ${PACKAGE_ast_INCLUDE}/times.h implicit dontcare
 							prev ${PACKAGE_ast_INCLUDE}/ast_time.h implicit dontcare
 							prev ${PACKAGE_ast_INCLUDE}/ast.h
@@ -436,7 +435,7 @@ make install virtual
 				make bltins/sleep.c
 					make FEATURE/poll implicit
 						prev features/poll
-						exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} : run features/poll
+						exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/poll
 					done FEATURE/poll
 					prev FEATURE/time
 					prev include/builtins.h
@@ -492,7 +491,7 @@ make install virtual
 					make include/ulimit.h implicit
 						make FEATURE/rlimits implicit
 							prev features/rlimits
-							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} : run features/rlimits
+							exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/rlimits
 						done FEATURE/rlimits
 						prev FEATURE/time
 					done include/ulimit.h
@@ -1031,7 +1030,7 @@ make install virtual
 						make features/math.sh
 							prev data/math.tab implicit
 						done features/math.sh
-						exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libm} ${mam_libnsl} -lm : run features/math.sh ${PACKAGEROOT}/src/cmd/ksh93/data/math.tab
+						exec - iffe ${IFFEFLAGS} -v -c "${CC} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS}" ref ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -I${PACKAGE_ast_INCLUDE} -I${INSTALLROOT}/include ${mam_libdll} ${mam_libcmd} ${mam_libast} ${mam_libnsl} : run features/math.sh ${PACKAGEROOT}/src/cmd/ksh93/data/math.tab
 						prev ${PACKAGE_ast_INCLUDE}/ast_standards.h implicit
 						make ${INSTALLROOT}/src/lib/libast/FEATURE/float implicit
 							prev ${INSTALLROOT}/src/lib/libast/FEATURE/standards implicit
@@ -1163,7 +1162,7 @@ make install virtual
 			exec - (ranlib libshell.a) >/dev/null 2>&1 || true
 		done libshell.a
 		bind -lshell
-		exec - ${CC} ${CCLDFLAGS} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS} ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -o ksh pmain.o ${mam_libshell} ${mam_libnsl} ${mam_libast} -lm
+		exec - ${CC} ${CCLDFLAGS} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS} ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -o ksh pmain.o ${mam_libshell} ${mam_libnsl} ${mam_libast}
 	done ksh
 	make shcomp
 		make shcomp.o
@@ -1179,7 +1178,7 @@ make install virtual
 			exec - ${CC} ${mam_cc_FLAGS} ${CCFLAGS} -I. -Iinclude -I${PACKAGE_ast_INCLUDE} -DSH_DICT=${SH_DICT} -D_API_ast=20100309 -DERROR_CONTEXT_T=Error_context_t -c sh/shcomp.c
 		done shcomp.o
 		prev ksh
-		exec - ${CC} ${CCLDFLAGS} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS} ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -o shcomp shcomp.o ${mam_libshell} ${mam_libnsl} ${mam_libast} -lm
+		exec - ${CC} ${CCLDFLAGS} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS} ${mam_cc_L+-L.} ${mam_cc_L+-L${INSTALLROOT}/lib} -o shcomp shcomp.o ${mam_libshell} ${mam_libnsl} ${mam_libast}
 	done shcomp
 	make shell virtual
 		prev libshell.a
diff --git a/src/lib/libast/Mamfile b/src/lib/libast/Mamfile
index 6842b798686d..181f51e61439 100644
--- a/src/lib/libast/Mamfile
+++ b/src/lib/libast/Mamfile
@@ -272,6 +272,7 @@ make install virtual
 				note * generate initial ast.req
 				note *
 				prev ${INSTALLROOT}/bin/mkreq
+				exec - set -o errexit
 				exec - mkreq ${CC} ${mam_cc_FLAGS} ${CCFLAGS} : ${LDFLAGS} : ast iconv w
 				note *
 				note * some systems move -lc routines to -lm; see astmath.c for details
@@ -281,13 +282,15 @@ make install virtual
 						prev std/endian.h
 					done port/astmath.c
 					exec - X=1
-					exec - for N in 1 2 3 4 5 6 8
+					exec - for N in 1 2 3 4 5 6 7 8
 					exec - do	if	${CC} ${CCLDFLAGS} -DN=$N -DIS ${mam_cc_FLAGS} ${CCFLAGS} -I. -Istd ${LDFLAGS} -o astmath.exe port/astmath.c 2>/dev/null
 					exec -		then	: implicit math function N=$N :
 					exec -		elif	${CC} ${CCLDFLAGS} -DN=$N -DIS ${mam_cc_FLAGS} ${CCFLAGS} -I. -Istd ${LDFLAGS} -o astmath.exe port/astmath.c -lm 2>/dev/null
 					exec -		then	: math function N=$N requires -lm :
 					exec -			X=0
 					exec -			break
+					exec -		else	: ERROR: astmath.c fails to compile or link, even with -lm :
+					exec -			exit 1
 					exec -		fi
 					exec - done
 					exec - ${STDRM} -rf astmath.exe*
@@ -295,7 +298,8 @@ make install virtual
 				done astmath.out
 				prev FEATURE/aso
 				exec - sed -e '/^#define _REQ_/!d' -e 's/#define _REQ_\([a-z0-9_]*\).*/ -l\1/' FEATURE/aso >> ast.req
-				exec - case $(${STDCAT} astmath.out) in
+				exec - read no_libm_needed <astmath.out
+				exec - case $no_libm_needed in
 				exec - 0)	echo ' -lm' >> ast.req ;;
 				exec - *)	touch ast.req ;;
 				exec - esac
@@ -4989,6 +4993,7 @@ make install virtual
 			exec - ${CC} ${mam_cc_FLAGS} ${CCFLAGS} -I${INSTALLROOT}/include/ast -D_PACKAGE_ast -c ${PACKAGEROOT}/src/cmd/INIT/mamake.c
 		done mamake.o
 		bind -last
+		exec - set -o errexit
 		exec - ${CC} ${CCLDFLAGS} ${mam_cc_FLAGS} ${CCFLAGS} ${LDFLAGS} ${mam_cc_L+-L${INSTALLROOT}/lib} -o mamake mamake.o ${mam_libast}
 		note *
 		note * We purposely do not have a make target of ${INSTALLROOT}/bin/mamake here;
diff --git a/src/lib/libast/port/astmath.c b/src/lib/libast/port/astmath.c
index 917a5de2d467..5e6afe47025c 100644
--- a/src/lib/libast/port/astmath.c
+++ b/src/lib/libast/port/astmath.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                  *
 *                                                                      *
@@ -20,27 +20,33 @@
 /*
  * used to test if -last requires -lm
  *
- *	arch		-last			-lm
- *	----		-----			---
- *	linux.sparc	sfdlen,sfputd		frexp,ldexp	
+ * This program is compiled and linked from a probe script in libast/Mamfile
+ * but never actually run. It is only used to check if linking succeeds
+ * without or with -lm.
+ *
+ * For that test to work correctly, we must work around compiler optimization.
+ * The rand() calls are to stop the result from being considered known at
+ * compile time, which would cause modern compilers to optimize out the probe
+ * calls, which would in turn cause linking to succeed where it shouldn't.
  */
 
 #if N >= 8
 #define _ISOC99_SOURCE	1
 #endif
 
+#include <stdlib.h>
 #include <math.h>
 
 int
 main(void)
 {
 #if N & 1
-	long double	value = 0;
+	long double	value = rand();
 #else
-	double		value = 0;
+	double		value = rand();
 #endif
 #if N < 5
-	int		exp = 0;
+	int		exp = rand();
 #endif
 
 #if N == 1