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Re: [PATCH] LD: PROVIDE_HIDDEN export class problem
- From: "Maciej W. Rozycki" <macro at codesourcery dot com>
- To: Alan Modra <amodra at gmail dot com>
- Cc: "Joseph S. Myers" <joseph at codesourcery dot com>, Dave Anglin <dave dot anglin at nrc dot ca>, Jeff Law <law at redhat dot com>, <binutils at sourceware dot org>
- Date: Thu, 2 May 2013 22:13:17 +0100
- Subject: Re: [PATCH] LD: PROVIDE_HIDDEN export class problem
- References: <alpine dot DEB dot 1 dot 10 dot 1304292220350 dot 1453 at tp dot orcam dot me dot uk> <20130430012124 dot GA3074 at bubble dot grove dot modra dot org> <alpine dot DEB dot 1 dot 10 dot 1304300301170 dot 1453 at tp dot orcam dot me dot uk> <20130502013429 dot GH5221 at bubble dot grove dot modra dot org>
On Thu, 2 May 2013, Alan Modra wrote:
> > I hoped the test cases provided were clear enough an illustration,
> > however in this case perhaps a C code piece will be better. Given code
> > produced from a definition like this:
> >
> > int foo = 1234;
> >
> > present in input and a linker script containing:
> >
> > PROVIDE_HIDDEN (foo = bar);
> >
> > I see no reason why foo should be assigned the hidden export class, as in
> > this case "the linker will silently use the definition in the program."
> > Likewise I'd expect the link not to fail even if there's been no bar
> > definition anywhere.
>
> Why would someone use PROVIDE_HIDDEN rather than plain PROVIDE if
> they don't want "foo" hidden?
>
> > Do you have a reference backing your claim that my interpretation is
> > wrong?
>
> Well, the current ld info doc says of PROVIDE_HIDDEN: "Similar to
> PROVIDE. For ELF targeted ports, the symbol will be hidden and won't
> be exported." Notice that it doesn't say "will be hidden .. if
> provided". Hiding the symbol is unconditional according to the way I
> read this.
>
> Furthermore, I think the current behaviour is not really surprising,
> given that not just a definition but even a reference (undefined
> symbol) with STV_HIDDEN in a relocatable object file results in the
> output symbol being hidden.
I don't feel particularly convinced, although I do recognise the pros
you've noted. What I think the case is the current semantics wasn't
really architected and just happened as a side effect of the original
implementation of PROVIDE_HIDDEN support. I don't feel compelled to argue
to death either.
But in any case I think at least the properties of this command should be
properly covered in testing so as to avoid future surprises. Here's the
test script and cases I offered previously modified suitably to cover the
current semantics. No regressions across the usual 139 targets.
OK to apply?
2013-05-02 Maciej W. Rozycki <macro@codesourcery.com>
ld/testsuite/
* ld-elf/provide-hidden-s.nd: New test.
* ld-elf/provide-hidden-abs.nd: New test.
* ld-elf/provide-hidden-def.nd: New test.
* ld-elf/provide-hidden-dyn.nd: New test.
* ld-elf/provide-hidden-sec.nd: New test.
* ld-elf/provide-hidden-dynabs.nd: New test.
* ld-elf/provide-hidden-dynsec.nd: New test.
* ld-elf/provide-hidden-s.ld: New test linker script.
* ld-elf/provide-hidden-1.ld: New test linker script.
* ld-elf/provide-hidden-2.ld: New test linker script.
* ld-elf/provide-hidden-1.s: New test source.
* ld-elf/provide-hidden-2.s: New test source.
* ld-elf/provide-hidden-3.s: New test source.
* ld-elf/provide-hidden-4.s: New test source.
* ld-elf/provide-hidden.exp: New test script.
Maciej
binutils-provide-hidden-test.diff
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-1.ld
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-1.ld 2013-05-02 14:42:21.583869464 +0100
@@ -0,0 +1,15 @@
+SECTIONS
+{
+ . = 0x12300000;
+ .data :
+ {
+ PROVIDE_HIDDEN (foo = . + 0x11100000);
+ *(.data)
+ }
+ .got : { *(.got) }
+ .interp : { *(.interp) }
+ .dynsym : { *(.dynsym) }
+ .dynstr : { *(.dynstr) }
+ .dynamic : { *(.dynamic) }
+ .hash : { *(.hash) }
+}
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-1.s
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-1.s 2013-05-02 14:42:21.583869464 +0100
@@ -0,0 +1,4 @@
+ .data
+ .globl foo
+foo:
+ .dc.a foo
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-2.ld
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-2.ld 2013-05-02 14:42:21.583869464 +0100
@@ -0,0 +1,12 @@
+SECTIONS
+{
+ . = 0x12300000;
+ PROVIDE_HIDDEN (foo = . + 0x11100000);
+ .data : { *(.data) }
+ .got : { *(.got) }
+ .interp : { *(.interp) }
+ .dynsym : { *(.dynsym) }
+ .dynstr : { *(.dynstr) }
+ .dynamic : { *(.dynamic) }
+ .hash : { *(.hash) }
+}
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-2.s
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-2.s 2013-05-02 14:42:21.583869464 +0100
@@ -0,0 +1,5 @@
+ .data
+ .globl foo
+ .internal foo
+foo:
+ .dc.a foo
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-3.s
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-3.s 2013-05-02 14:42:21.583869464 +0100
@@ -0,0 +1,4 @@
+ .data
+ .globl bar
+bar:
+ .dc.a foo
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-4.s
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-4.s 2013-05-02 14:42:21.583869464 +0100
@@ -0,0 +1,5 @@
+ .data
+ .globl bar
+ .internal foo
+bar:
+ .dc.a foo
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-abs.nd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-abs.nd 2013-05-02 15:42:59.052764874 +0100
@@ -0,0 +1,5 @@
+#...
+Symbol table '\.symtab' contains [0-9]+ entries:
+#...
+ *[0-9]+: 0*23400000 +0 (?:NOTYPE|OBJECT) +LOCAL +DEFAULT +ABS foo
+#pass
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-def.nd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-def.nd 2013-05-02 14:42:21.583869464 +0100
@@ -0,0 +1,5 @@
+#...
+Symbol table '\.symtab' contains [0-9]+ entries:
+#...
+ *[0-9]+: 0*12300000 +0 (?:NOTYPE|OBJECT) +LOCAL +DEFAULT +[0-9]+ foo
+#pass
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-dyn.nd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-dyn.nd 2013-05-02 17:56:59.082900096 +0100
@@ -0,0 +1,7 @@
+#failif
+Symbol table '\.dynsym' contains [0-9]+ entries:
+#...
+.* foo
+#...
+Symbol table '\.symtab' contains [0-9]+ entries:
+#pass
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-dynabs.nd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-dynabs.nd 2013-05-02 20:36:07.312653925 +0100
@@ -0,0 +1,8 @@
+Symbol table '\.dynsym' contains [0-9]+ entries:
+#...
+ *[0-9]+: 0*23400000 +0 (?:NOTYPE|OBJECT) +LOCAL +DEFAULT +ABS foo
+#...
+Symbol table '\.symtab' contains [0-9]+ entries:
+#...
+ *[0-9]+: 0*23400000 +0 (?:NOTYPE|OBJECT) +LOCAL +DEFAULT +ABS foo
+#pass
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-dynsec.nd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-dynsec.nd 2013-05-02 20:12:53.633868977 +0100
@@ -0,0 +1,8 @@
+Symbol table '\.dynsym' contains [0-9]+ entries:
+#...
+ *[0-9]+: 0*23400000 +0 (?:NOTYPE|OBJECT) +LOCAL +DEFAULT +[0-9]+ foo
+#...
+Symbol table '\.symtab' contains [0-9]+ entries:
+#...
+ *[0-9]+: 0*23400000 +0 (?:NOTYPE|OBJECT) +LOCAL +DEFAULT +[0-9]+ foo
+#pass
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-s.ld
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-s.ld 2013-05-02 15:50:02.603231709 +0100
@@ -0,0 +1,11 @@
+SECTIONS
+{
+ . = 0x12300000;
+ .data : { *(.data) }
+ .got : { *(.got) }
+ .interp : { *(.interp) }
+ .dynsym : { *(.dynsym) }
+ .dynstr : { *(.dynstr) }
+ .dynamic : { *(.dynamic) }
+ .hash : { *(.hash) }
+}
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-s.nd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-s.nd 2013-05-02 15:48:41.592760597 +0100
@@ -0,0 +1,8 @@
+Symbol table '\.dynsym' contains [0-9]+ entries:
+#...
+ *[0-9]+: 0*12300000 +0 (?:NOTYPE|OBJECT) +GLOBAL +DEFAULT +[0-9]+ foo
+#...
+Symbol table '\.symtab' contains [0-9]+ entries:
+#...
+ *[0-9]+: 0*12300000 +0 (?:NOTYPE|OBJECT) +GLOBAL +DEFAULT +[0-9]+ foo
+#pass
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-sec.nd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden-sec.nd 2013-05-02 15:42:54.552761072 +0100
@@ -0,0 +1,5 @@
+#...
+Symbol table '\.symtab' contains [0-9]+ entries:
+#...
+ *[0-9]+: 0*23400000 +0 (?:NOTYPE|OBJECT) +LOCAL +DEFAULT +[0-9]+ foo
+#pass
Index: binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden.exp
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils-fsf-trunk-quilt/ld/testsuite/ld-elf/provide-hidden.exp 2013-05-02 20:36:37.812655868 +0100
@@ -0,0 +1,154 @@
+# Expect script for the PROVIDE_HIDDEN linker script command.
+#
+# Copyright 2013 Free Software Foundation, Inc.
+#
+# This file is part of the GNU Binutils.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+# MA 02110-1301, USA.
+#
+
+#
+# Written by Maciej W. Rozycki <macro@codesourcery.com>
+#
+
+# Export classes only make sense for ELF shared-library targets.
+if { ![is_elf_format] || ![check_shared_lib_support] } {
+ return
+}
+
+# This target requires extra GAS options when building code for shared
+# libraries.
+set AFLAGS_PIC ""
+if [istarget "tic6x-*-*"] {
+ append AFLAGS_PIC " -mpic -mpid=near"
+}
+
+set testname "PROVIDE_HIDDEN test"
+
+run_ld_link_tests [list \
+ [list \
+ "$testname (auxiliary shared object)" \
+ "-shared -T provide-hidden-s.ld" "" \
+ "$AFLAGS_PIC" \
+ [list provide-hidden-1.s ] \
+ [list "readelf -s provide-hidden-s.nd"] \
+ "provide-hidden-s.so"]]
+
+run_ld_link_tests [list \
+ [list \
+ "$testname 1" \
+ "-T provide-hidden-1.ld" "" \
+ "" \
+ [list provide-hidden-1.s] \
+ [list \
+ [list readelf -s provide-hidden-def.nd] \
+ [list readelf -s provide-hidden-dyn.nd]] \
+ "provide-hidden-1"] \
+ [list \
+ "$testname 2" \
+ "-T provide-hidden-1.ld" "" \
+ "" \
+ [list provide-hidden-2.s] \
+ [list \
+ [list readelf -s provide-hidden-def.nd] \
+ [list readelf -s provide-hidden-dyn.nd]] \
+ "provide-hidden-2"] \
+ [list \
+ "$testname 3" \
+ "-T provide-hidden-1.ld" "" \
+ "" \
+ [list provide-hidden-3.s] \
+ [list \
+ [list readelf -s provide-hidden-sec.nd] \
+ [list readelf -s provide-hidden-dyn.nd]] \
+ "provide-hidden-3"] \
+ [list \
+ "$testname 4" \
+ "-T provide-hidden-1.ld" "tmpdir/provide-hidden-s.so" \
+ "" \
+ [list provide-hidden-3.s] \
+ [list "readelf -s provide-hidden-dynsec.nd"] \
+ "provide-hidden-4"] \
+ [list \
+ "$testname 5" \
+ "-T provide-hidden-1.ld" "" \
+ "" \
+ [list provide-hidden-4.s] \
+ [list \
+ [list readelf -s provide-hidden-sec.nd] \
+ [list readelf -s provide-hidden-dyn.nd]] \
+ "provide-hidden-5"] \
+ [list \
+ "$testname 6" \
+ "-T provide-hidden-1.ld" "tmpdir/provide-hidden-s.so" \
+ "" \
+ [list provide-hidden-4.s] \
+ [list \
+ [list readelf -s provide-hidden-sec.nd] \
+ [list readelf -s provide-hidden-dyn.nd]] \
+ "provide-hidden-6"] \
+ [list \
+ "$testname 7" \
+ "-T provide-hidden-2.ld" "" \
+ "" \
+ [list provide-hidden-1.s] \
+ [list \
+ [list readelf -s provide-hidden-def.nd] \
+ [list readelf -s provide-hidden-dyn.nd]] \
+ "provide-hidden-7"] \
+ [list \
+ "$testname 8" \
+ "-T provide-hidden-2.ld" "" \
+ "" \
+ [list provide-hidden-2.s] \
+ [list \
+ [list readelf -s provide-hidden-def.nd] \
+ [list readelf -s provide-hidden-dyn.nd]] \
+ "provide-hidden-8"] \
+ [list \
+ "$testname 9" \
+ "-T provide-hidden-2.ld" "" \
+ "" \
+ [list provide-hidden-3.s] \
+ [list \
+ [list readelf -s provide-hidden-abs.nd] \
+ [list readelf -s provide-hidden-dyn.nd]] \
+ "provide-hidden-9"] \
+ [list \
+ "$testname 10" \
+ "-T provide-hidden-2.ld" "tmpdir/provide-hidden-s.so" \
+ "" \
+ [list provide-hidden-3.s] \
+ [list "readelf -s provide-hidden-dynabs.nd"] \
+ "provide-hidden-10"] \
+ [list \
+ "$testname 11" \
+ "-T provide-hidden-2.ld" "" \
+ "" \
+ [list provide-hidden-4.s] \
+ [list \
+ [list readelf -s provide-hidden-abs.nd] \
+ [list readelf -s provide-hidden-dyn.nd]] \
+ "provide-hidden-11"] \
+ [list \
+ "$testname 12" \
+ "-T provide-hidden-2.ld" "tmpdir/provide-hidden-s.so" \
+ "" \
+ [list provide-hidden-4.s] \
+ [list \
+ [list readelf -s provide-hidden-abs.nd] \
+ [list readelf -s provide-hidden-dyn.nd]] \
+ "provide-hidden-12"]]