Treat common symbol in executable as definition

Common symbol in executable is a definition, which overrides definition
from shared objects.  When linker sees a new definition from a shared
object, the new dynamic definition should be overridden by the previous
common symbol in executable.

bfd/

	PR ld/19579
	* elflink.c (_bfd_elf_merge_symbol): Treat common symbol in
	executable as definition if the new definition comes from a
	shared library.

ld/

	PR ld/19579
	* testsuite/ld-elf/pr19579a.c: New file.
	* testsuite/ld-elf/pr19579b.c: Likewise.
	* testsuite/ld-elf/shared.exp: Run PR ld/19579 test.

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index b2cc5b85ba254834bf177b00da65f6f1b539db66..5f9f99d62f87da4e41487debf37182617a8d1944 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,10 @@
+2016-03-04  H.J. Lu  <hongjiu.lu@intel.com>
+
+       PR ld/19579
+       * elflink.c (_bfd_elf_merge_symbol): Treat common symbol in
+       executable as definition if the new definition comes from a
+       shared library.
+
 2016-03-02  Alan Modra  <amodra@gmail.com>
 
        * Makefile.in: Regenerate.

diff --git a/bfd/elflink.c b/bfd/elflink.c
index 0e3abff5ce4aef94767dd2863f042104c331c429..39157bf77894ddd365c6c7c682c57270114ce050 100644 (file)
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -1172,9 +1172,12 @@ _bfd_elf_merge_symbol (bfd *abfd,
 
   newdef = !bfd_is_und_section (sec) && !bfd_is_com_section (sec);
 
+  /* The old common symbol in executable is a definition if the new
+     definition comes from a shared library.  */
   olddef = (h->root.type != bfd_link_hash_undefined
            && h->root.type != bfd_link_hash_undefweak
-           && h->root.type != bfd_link_hash_common);
+           && (h->root.type != bfd_link_hash_common
+               || (!olddyn && newdyn && bfd_link_executable (info))));
 
   /* NEWFUNC and OLDFUNC indicate whether the new or old symbol,
      respectively, appear to be a function.  */

diff --git a/ld/ChangeLog b/ld/ChangeLog
index 328e51d85b2e08cb1d011760b93dc0c473c08874..ac73cf8a20cccdf3591ac20f5a49cb3f19a1268d 100644 (file)
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,10 @@
+2016-03-04  H.J. Lu  <hongjiu.lu@intel.com>
+
+       PR ld/19579
+       * testsuite/ld-elf/pr19579a.c: New file.
+       * testsuite/ld-elf/pr19579b.c: Likewise.
+       * testsuite/ld-elf/shared.exp: Run PR ld/19579 test.
+
 2016-03-02  H.J. Lu  <hongjiu.lu@intel.com>
 
        * testsuite/ld-elf/pr19162.d: Skip hppa-*-*.

diff --git a/ld/testsuite/ld-elf/pr19579a.c b/ld/testsuite/ld-elf/pr19579a.c
new file mode 100644 (file)
index 0000000..e4a6eb1
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr19579a.c
@@ -0,0 +1,15 @@
+#include <stdio.h>
+
+int foo[1];
+int bar[2];
+
+extern int *foo_p (void);
+extern int *bar_p (void);
+
+int
+main ()
+{
+  if (foo[0] == 0 && foo == foo_p () && bar[0] == 0 && bar == bar_p ())
+    printf ("PASS\n");
+  return 0;
+}

diff --git a/ld/testsuite/ld-elf/pr19579b.c b/ld/testsuite/ld-elf/pr19579b.c
new file mode 100644 (file)
index 0000000..d906545
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr19579b.c
@@ -0,0 +1,14 @@
+int foo[2];
+int bar[2] = { -1, -1 };
+
+int *
+foo_p (void)
+{
+  return foo;
+}
+
+int *
+bar_p (void)
+{
+  return bar;
+}

diff --git a/ld/testsuite/ld-elf/shared.exp b/ld/testsuite/ld-elf/shared.exp
index 678ab1bb31f8169760128cb16551c3fbdedd07b1..ef0747d610babf816ee9940d2c85d72d54d3a2ee 100644 (file)
--- a/ld/testsuite/ld-elf/shared.exp
+++ b/ld/testsuite/ld-elf/shared.exp
@@ -524,6 +524,21 @@ if { [istarget *-*-linux*]
            {} \
            "libpr2404b.a" \
        ] \
+       [list \
+           "Build pr19579a.o" \
+           "" "-fPIE" \
+           {pr19579a.c} \
+           {} \
+           "libpr19579a.a" \
+       ] \
+       [list \
+           "Build libpr19579.so" \
+           "-shared" \
+           "-fPIC" \
+           {pr19579b.c} \
+           {} \
+           "libpr19579.so" \
+       ] \
     ]
     run_ld_link_exec_tests [] [list \
        [list \
@@ -580,6 +595,15 @@ if { [istarget *-*-linux*]
            "pass.out" \
            "-O2 -fPIC -I../bfd" \
        ] \
+       [list \
+           "Run pr19579" \
+           "-pie -z text tmpdir/pr19579a.o tmpdir/libpr19579.so" \
+           "" \
+           {dummy.c} \
+           "pr19579" \
+           "pass.out" \
+           "-fPIE" \
+       ] \
     ]
 }