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 1c5d4db19d617f4583e4130650a5be93e686d0f0..dde5080232a37eeb9f4fa755f0d1239541773144 100755 (executable)
--- a/configure
+++ b/configure
@@ -11399,9 +11399,12 @@ 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
@@ -11414,11 +11417,11 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 #ifdef __cplusplus
 extern "C"
 #endif
-char dlopen ();
+char dlsym ();
 int
 main ()
 {
-return dlopen ();
+return dlsym ();
   ;
   return 0;
 }
@@ -11431,25 +11434,25 @@ for ac_lib in '' dl; do
     LIBS="-l$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 7cd1d91672fd4a736f4e764cb40a83a1cd6d9664..48103f35e287c1e76d3c0e0c7464526597ee8645 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -1178,7 +1178,10 @@ 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])