[binutils-gdb] [gdb/testsuite] Compile compile-ifunc.c with -Wno-attribute-alias

[gdb-buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 6173d6a696349bd934166b4694c24f4eda7362c0 ***

commit 6173d6a696349bd934166b4694c24f4eda7362c0
Author:     Tom de Vries <tdevries@suse.de>
AuthorDate: Wed May 6 05:27:48 2020 +0200
Commit:     Tom de Vries <tdevries@suse.de>
CommitDate: Wed May 6 05:27:48 2020 +0200

    [gdb/testsuite] Compile compile-ifunc.c with -Wno-attribute-alias
    
    Consider the following test-case:
    ...
    $ cat 1.c
    typedef int (*final_t) (int arg);
    int final (int arg)
      { return arg + 1; }
    final_t gnu_ifunc (void)
      { return final; }
    int gnu_ifunc_alias (int) __attribute__ ((ifunc ("gnu_ifunc")));
    int main (void)
      { return gnu_ifunc_alias (10); }
    ...
    with result:
    ...
    $ gcc 1.c
    $ ./a.out; echo $?
    11
    ...
    
    The test-case uses the ifunc attribute, but there's another solution using
    %gnu_indirect_function.  Consider 2.c and 3.c:
    ...
    $ cat 2.c
    typedef int (*final_t) (int arg);
    int final (int arg)
      { return arg + 1; }
    asm (".type gnu_ifunc, %gnu_indirect_function");
    final_t gnu_ifunc (void)
      { return final; }
    $ cat 3.c
    extern int gnu_ifunc (int);
    int main (void)
      { return gnu_ifunc (10); }
    ...
    
    However, it can be inconvenient to have seperate files for the incompatible
    decls of gnu_ifunc, so we can use this in a single file like this:
    ...
    $ cat 4.c
    typedef int (*final_t) (int arg);
    int final (int arg)
      { return arg + 1; }
    asm (".type gnu_ifunc, %gnu_indirect_function");
    final_t gnu_ifunc (void)
      { return final; }
    extern int gnu_ifunc_alias (int arg) __attribute__ ((alias ("gnu_ifunc")));
    int main (void)
      { return gnu_ifunc_alias (10); }
    ...
    
    This alias trick works ok at -O0, but not at -O2:
    ...
    $ gcc 4.c
    $ ./a.out; echo $?
    11
    $ gcc 4.c
    $ ./a.out; echo $?
    176
    ...
    and produces a warning with gcc-8 and later:
    ...
    $ gcc-8 4.c
    4.c:7:12: warning: 'gnu_ifunc_alias' alias between functions of incompatible \
      types 'int(int)' and 'int (*(void))(int)' [-Wattribute-alias]
     extern int gnu_ifunc_alias (int arg) __attribute__ ((alias ("gnu_ifunc")));
                ^~~~~~~~~~~~~~~
    4.c:5:9: note: aliased declaration here
     final_t gnu_ifunc (void)
             ^~~~~~~~~
    ...
    The warning is correct, but the mismatch is intentional.
    
    The last variant (%gnu_indirect_function + alias) is used in
    gdb.compile/compile-ifunc.c, so we run into the warning with recent gcc.
    
    Fix the warning by compiling with -Wno-attribute-alias.
    
    Tested the test-case on x86_64-linux with gcc-10, and observed I no longer see
    the warning:
    ...
    Running src/gdb/testsuite/gdb.compile/compile-ifunc.exp ...
    
                    === gdb Summary ===
    
    nr of untested testcases         1
    ...
    
    gdb/testsuite/ChangeLog:
    
    2020-05-06  Tom de Vries  <tdevries@suse.de>
    
            * gdb.compile/compile-ifunc.exp: Use -Wno-attribute-alias.

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 409f44ca9d..7b88b3a469 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2020-05-06  Tom de Vries  <tdevries@suse.de>
+
+	* gdb.compile/compile-ifunc.exp: Use -Wno-attribute-alias.
+
 2020-05-04  Tom de Vries  <tdevries@suse.de>
 
 	* gdb.base/async.exp: Check whether instruction addresses are a
diff --git a/gdb/testsuite/gdb.compile/compile-ifunc.exp b/gdb/testsuite/gdb.compile/compile-ifunc.exp
index ff81e2f87a..9239c5adf1 100644
--- a/gdb/testsuite/gdb.compile/compile-ifunc.exp
+++ b/gdb/testsuite/gdb.compile/compile-ifunc.exp
@@ -19,9 +19,16 @@ if {[skip_ifunc_tests]} {
 
 standard_testfile
 
+get_compiler_info
+set flags ""
+if [test_compiler_info gcc*] {
+    set flags additional_flags=-Wno-attribute-alias
+}
+
 with_test_prefix "nodebug" {
 
-    if { [prepare_for_testing "failed to prepare" "$testfile-nodebug" $srcfile {}] } {
+    if { [prepare_for_testing "failed to prepare" "$testfile-nodebug" \
+	      $srcfile $flags] } {
 	return -1
     }
 
@@ -51,7 +58,8 @@ with_test_prefix "nodebug" {
 
 with_test_prefix "debug" {
 
-    if { [prepare_for_testing "failed to prepare" "$testfile-debug" $srcfile] } {
+    if { [prepare_for_testing "failed to prepare" "$testfile-debug" \
+	      $srcfile "debug $flags"] } {
 	return -1
     }