configure: check for dlsym instead of dlopen.

When building with sanitizers the sanitizer library provides dlopen, but not
dlsym(), making configure think that -ldl isn't needed. Just checking for
dlsym() ought to suffice, hard to see dlsym() being provided without dlopen()
also being provided.

Backpatch to all branches, for the same reasons as 46ab07ffda9.

Reviewed-By: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/20220323173537.ll7klrglnp4gn2um@alap3.anarazel.de
Backpatch: 10-

diff --git a/configure b/configure
index 356770e00f2936865c9fd0215594bd31a67d0cfb..fedd666e81b13d6f1a34ae3029cb5f0f524028b3 100755 (executable)
--- a/configure
+++ b/configure
@@ -10925,9 +10925,12 @@ if test "$ac_res" != no; then :
 
 fi
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing dlopen" >&5
-$as_echo_n "checking for library containing dlopen... " >&6; }
-if ${ac_cv_search_dlopen+:} false; then :
+# gcc/clang's sanitizer helper library provides dlopen but not dlsym, thus
+# when enabling asan the dlopen check doesn't notice that -ldl is actually
+# required. Just checking for dlsym() ought to suffice.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing dlsym" >&5
+$as_echo_n "checking for library containing dlsym... " >&6; }
+if ${ac_cv_search_dlsym+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   ac_func_search_save_LIBS=$LIBS
@@ -10940,11 +10943,11 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 #ifdef __cplusplus
 extern "C"
 #endif
-char dlopen ();
+char dlsym ();
 int
 main ()
 {
-return dlopen ();
+return dlsym ();
   ;
   return 0;
 }
@@ -10957,25 +10960,25 @@ for ac_lib in '' dl; do
     LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
   fi
   if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_search_dlopen=$ac_res
+  ac_cv_search_dlsym=$ac_res
 fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext
-  if ${ac_cv_search_dlopen+:} false; then :
+  if ${ac_cv_search_dlsym+:} false; then :
   break
 fi
 done
-if ${ac_cv_search_dlopen+:} false; then :
+if ${ac_cv_search_dlsym+:} false; then :
 
 else
-  ac_cv_search_dlopen=no
+  ac_cv_search_dlsym=no
 fi
 rm conftest.$ac_ext
 LIBS=$ac_func_search_save_LIBS
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_dlopen" >&5
-$as_echo "$ac_cv_search_dlopen" >&6; }
-ac_res=$ac_cv_search_dlopen
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_dlsym" >&5
+$as_echo "$ac_cv_search_dlsym" >&6; }
+ac_res=$ac_cv_search_dlsym
 if test "$ac_res" != no; then :
   test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
 

diff --git a/configure.in b/configure.in
index fcc64b28a1f29a57f5f4f8542dffa59bfdf998d0..36f05b8087939bfba47c05bca68925da307f20da 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -1184,7 +1184,10 @@ AC_SUBST(PTHREAD_LIBS)
 
 AC_CHECK_LIB(m, main)
 AC_SEARCH_LIBS(setproctitle, util)
-AC_SEARCH_LIBS(dlopen, dl)
+# gcc/clang's sanitizer helper library provides dlopen but not dlsym, thus
+# when enabling asan the dlopen check doesn't notice that -ldl is actually
+# required. Just checking for dlsym() ought to suffice.
+AC_SEARCH_LIBS(dlsym, dl)
 AC_SEARCH_LIBS(socket, [socket ws2_32])
 AC_SEARCH_LIBS(shl_load, dld)
 # We only use libld in port/dynloader/aix.c