diff --git a/configure.ac b/configure.ac
index aa08c37e..cb6eaaa3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1015,11 +1015,15 @@ AC_CHECK_DECL([_mm_movemask_epi8],
 #
 # If everything above is supported, runtime detection will be used to keep the
 # binaries working on systems that don't support the required extensions.
+#
+# NOTE: Use a check that links and not merely compiles to ensure that
+# missing intrinsics don't get accepted with compilers that allow
+# implicit function declarations.
 AC_MSG_CHECKING([if _mm_clmulepi64_si128 is usable])
 AS_IF([test "x$enable_clmul_crc" = xno], [
 	AC_MSG_RESULT([no, --disable-clmul-crc was used])
 ], [
-	AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+	AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #include <immintrin.h>
 
 // CLMUL works on older E2K instruction set but it is slow due to emulation.
@@ -1131,7 +1135,7 @@ AS_CASE([$enable_sandbox],
 		# A compile check is done here because some systems have
 		# linux/landlock.h, but do not have the syscalls defined
 		# in order to actually use Linux Landlock.
-		AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+		AC_LINK_IFELSE([AC_LANG_SOURCE([[
 			#include <linux/landlock.h>
 			#include <sys/syscall.h>
 			#include <sys/prctl.h>
diff --git a/m4/tuklib_cpucores.m4 b/m4/tuklib_cpucores.m4
index a228a8fb..928ef344 100644
--- a/m4/tuklib_cpucores.m4
+++ b/m4/tuklib_cpucores.m4
@@ -71,7 +71,7 @@ main(void)
 # -lfreebsd-glue when linking and thus in the current form this would
 # fail on GNU/kFreeBSD. The above test for sched_getaffinity() matches
 # on GNU/kFreeBSD so the test below should never run on that OS.
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #include <sys/param.h>
 #include <sys/cpuset.h>
 
@@ -92,7 +92,7 @@ main(void)
 #
 # We test sysctl() first and intentionally break the sysctl() test on QNX
 # so that sysctl() is never used on QNX.
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #ifdef __QNX__
 compile error
 #endif
@@ -116,7 +116,7 @@ main(void)
 }
 ]])], [tuklib_cv_cpucores_method=sysctl], [
 
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #include <unistd.h>
 int
 main(void)
@@ -133,7 +133,7 @@ main(void)
 }
 ]])], [tuklib_cv_cpucores_method=sysconf], [
 
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #include <sys/param.h>
 #include <sys/pstat.h>
 
diff --git a/m4/tuklib_physmem.m4 b/m4/tuklib_physmem.m4
index b5e0b1ad..4bffe858 100644
--- a/m4/tuklib_physmem.m4
+++ b/m4/tuklib_physmem.m4
@@ -65,6 +65,11 @@ compile error
 # Look for AIX-specific solution before sysconf(), because the test
 # for sysconf() will pass on AIX but won't actually work
 # (sysconf(_SC_PHYS_PAGES) compiles but always returns -1 on AIX).
+#
+# NOTE: There is no need to link the check program because it's not calling
+# any functions and thus implicit function declarations aren't a problem.
+# The unused reference to _system_configuration.physmem might get optimized
+# away, and thus the linker might not see that symbol anyway.
 AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
 #include <sys/systemcfg.h>
 
@@ -76,7 +81,7 @@ main(void)
 }
 ]])], [tuklib_cv_physmem_method=aix], [
 
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #include <unistd.h>
 int
 main(void)
@@ -88,7 +93,7 @@ main(void)
 }
 ]])], [tuklib_cv_physmem_method=sysconf], [
 
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #ifdef HAVE_SYS_PARAM_H
 #	include <sys/param.h>
 #endif
@@ -104,7 +109,7 @@ main(void)
 }
 ]])], [tuklib_cv_physmem_method=sysctl], [
 
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #include <sys/sysinfo.h>
 #include <machine/hal_sysinfo.h>
 
@@ -118,7 +123,7 @@ main(void)
 }
 ]])], [tuklib_cv_physmem_method=getsysinfo],[
 
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #include <sys/param.h>
 #include <sys/pstat.h>
 
@@ -133,7 +138,7 @@ main(void)
 }
 ]])], [tuklib_cv_physmem_method=pstat_getstatic],[
 
-AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #include <invent.h>
 int
 main(void)
@@ -150,7 +155,7 @@ main(void)
 # different sysinfo() so we must check $host_os.
 case $host_os in
 	linux*)
-		AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+		AC_LINK_IFELSE([AC_LANG_SOURCE([[
 #include <sys/sysinfo.h>
 int
 main(void)