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 
Discussion: https://postgr.es/m/20220323173537[email protected]
Backpatch: 10-

diff --git a/configure b/configure
index 4267c7e1d5b7b8de3ff5b71005472fb7d9f22a90..5378edf1927ca5b27b6f80436ad79d86bf11a9a0 100755 (executable)
--- a/configure
+++ b/configure
@@ -11700,9 +11700,12 @@ 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
@@ -11715,11 +11718,11 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 #ifdef __cplusplus
 extern "C"
 #endif
-char dlopen ();
+char dlsym ();
 int
 main ()
 {
-return dlopen ();
+return dlsym ();
   ;
   return 0;
 }
@@ -11732,25 +11735,25 @@ for ac_lib in '' dl; do
     LIBS="-l$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.ac b/configure.ac
index 225e5afd8706dd78491c36d92c8cfb266c5df4b5..ade30046d6c87a533f6138f0c1a0e83a10a1e64c 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -1200,7 +1200,10 @@ 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)
 AC_SEARCH_LIBS(getopt_long, [getopt gnugetopt])