Revert [5215b8740c] (Enh [2959069]), as it turns out that -fvisibility=hidden only affects definitions and not declarations.

Therefore explicitely declaring each MODULE_SCOPE function as  __attribute__((__visibility__("hidden")) is much better. 
Suggested by Stuart Cassoff (Thanks!).

2 files changed, 10 insertions, 103 deletions

diff --git a/unix/configure b/unix/configure
index 06ff7a4..5009807 100755
--- a/unix/configure
+++ b/unix/configure
@@ -6490,80 +6490,6 @@ if test "${tcl_cv_cc_visibility_hidden+set}" = set; then
   echo $ECHO_N "(cached) $ECHO_C" >&6
 else
 
-	    if test "$SHARED_BUILD" = 1; then
-
-		hold_cflags=$CFLAGS; CFLAGS="$CFLAGS -fvisibility=hidden -Werror"
-		cat >conftest.$ac_ext <<_ACEOF
-/* confdefs.h.  */
-_ACEOF
-cat confdefs.h >>conftest.$ac_ext
-cat >>conftest.$ac_ext <<_ACEOF
-/* end confdefs.h.  */
-
-int
-main ()
-{
-#if !defined(__GNUC__) || __GNUC__ < 4
-#error visibility hidden is not supported for this compiler
-#endif
-
-  ;
-  return 0;
-}
-_ACEOF
-rm -f conftest.$ac_objext
-if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
-  (eval $ac_compile) 2>conftest.er1
-  ac_status=$?
-  grep -v '^ *+' conftest.er1 >conftest.err
-  rm -f conftest.er1
-  cat conftest.err >&5
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); } &&
-	 { ac_try='test -z "$ac_c_werror_flag"
-			 || test ! -s conftest.err'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; } &&
-	 { ac_try='test -s conftest.$ac_objext'
-  { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5
-  (eval $ac_try) 2>&5
-  ac_status=$?
-  echo "$as_me:$LINENO: \$? = $ac_status" >&5
-  (exit $ac_status); }; }; then
-  tcl_cv_cc_visibility_hidden=yes
-else
-  echo "$as_me: failed program was:" >&5
-sed 's/^/| /' conftest.$ac_ext >&5
-
-tcl_cv_cc_visibility_hidden=no
-fi
-rm -f conftest.err conftest.$ac_objext conftest.$ac_ext
-		CFLAGS=$hold_cflags
-
-else
-
-		tcl_cv_cc_visibility_hidden=no
-
-fi
-
-
-fi
-echo "$as_me:$LINENO: result: $tcl_cv_cc_visibility_hidden" >&5
-echo "${ECHO_T}$tcl_cv_cc_visibility_hidden" >&6
-    if test $tcl_cv_cc_visibility_hidden = yes; then
-
-	CFLAGS="$CFLAGS -fvisibility=hidden"
-
-cat >>confdefs.h <<\_ACEOF
-#define MODULE_SCOPE extern
-_ACEOF
-
-
-else
-
 	hold_cflags=$CFLAGS; CFLAGS="$CFLAGS -Werror"
 	cat >conftest.$ac_ext <<_ACEOF
 /* confdefs.h.  */
@@ -6614,7 +6540,10 @@ fi
 rm -f conftest.err conftest.$ac_objext \
       conftest$ac_exeext conftest.$ac_ext
 	CFLAGS=$hold_cflags
-	if test $tcl_cv_cc_visibility_hidden = yes; then
+fi
+echo "$as_me:$LINENO: result: $tcl_cv_cc_visibility_hidden" >&5
+echo "${ECHO_T}$tcl_cv_cc_visibility_hidden" >&6
+    if test $tcl_cv_cc_visibility_hidden = yes; then
 
 
 cat >>confdefs.h <<\_ACEOF
@@ -6630,9 +6559,6 @@ _ACEOF
 fi
 
 
-fi
-
-
     # Step 0.d: Disable -rpath support?
 
     echo "$as_me:$LINENO: checking if rpath support is requested" >&5
@@ -8145,7 +8071,6 @@ cat >>confdefs.h <<\_ACEOF
 #define MODULE_SCOPE __private_extern__
 _ACEOF
 
-		tcl_cv_cc_visibility_hidden=yes
 
 fi
 
diff --git a/unix/tcl.m4 b/unix/tcl.m4
index 194cf90..e3a0d15 100644
--- a/unix/tcl.m4
+++ b/unix/tcl.m4
@@ -1045,34 +1045,17 @@ AC_DEFUN([SC_CONFIG_CFLAGS], [
 
     AC_CACHE_CHECK([if compiler supports visibility "hidden"],
 	tcl_cv_cc_visibility_hidden, [
-	    AS_IF([test "$SHARED_BUILD" = 1], [
-		hold_cflags=$CFLAGS; CFLAGS="$CFLAGS -fvisibility=hidden -Werror"
-		AC_TRY_COMPILE(,[#if !defined(__GNUC__) || __GNUC__ < 4
-#error visibility hidden is not supported for this compiler
-#endif
-		], tcl_cv_cc_visibility_hidden=yes,
-		    tcl_cv_cc_visibility_hidden=no)
-		CFLAGS=$hold_cflags
-	    ], [
-		tcl_cv_cc_visibility_hidden=no
-	    ])
-    ])
-    AS_IF([test $tcl_cv_cc_visibility_hidden = yes], [
-	CFLAGS="$CFLAGS -fvisibility=hidden"
-	AC_DEFINE(MODULE_SCOPE, [extern], [No need to mark inidividual symbols as hidden])
-    ], [
 	hold_cflags=$CFLAGS; CFLAGS="$CFLAGS -Werror"
 	AC_TRY_LINK([
 	    extern __attribute__((__visibility__("hidden"))) void f(void);
 	    void f(void) {}], [f();], tcl_cv_cc_visibility_hidden=yes,
 	    tcl_cv_cc_visibility_hidden=no)
-	CFLAGS=$hold_cflags
-	AS_IF([test $tcl_cv_cc_visibility_hidden = yes], [
-	    AC_DEFINE(MODULE_SCOPE,
-		[extern __attribute__((__visibility__("hidden")))],
-		[Compiler support for module scope symbols])
-	    AC_DEFINE(HAVE_HIDDEN, [1], [Compiler support for module scope symbols])
-	])
+	CFLAGS=$hold_cflags])
+    AS_IF([test $tcl_cv_cc_visibility_hidden = yes], [
+	AC_DEFINE(MODULE_SCOPE,
+	    [extern __attribute__((__visibility__("hidden")))],
+	    [Compiler support for module scope symbols])
+	AC_DEFINE(HAVE_HIDDEN, [1], [Compiler support for module scope symbols])
     ])
 
     # Step 0.d: Disable -rpath support?
@@ -1638,7 +1621,6 @@ AC_DEFUN([SC_CONFIG_CFLAGS], [
 	    AS_IF([test "$tcl_cv_cc_visibility_hidden" != yes], [
 		AC_DEFINE(MODULE_SCOPE, [__private_extern__],
 		    [Compiler support for module scope symbols])
-		tcl_cv_cc_visibility_hidden=yes
 	    ])
 	    CC_SEARCH_FLAGS=""
 	    LD_SEARCH_FLAGS=""