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Re: [PATCH, GCC/LTO] Fix PR69866: LTO with def for weak alias in regular object file
- From: Thomas Preudhomme <thomas dot preudhomme at foss dot arm dot com>
- To: Richard Biener <rguenther at suse dot de>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
- Cc: Jan Hubicka <hubicka at ucw dot cz>
- Date: Thu, 9 Mar 2017 09:43:13 +0000
- Subject: Re: [PATCH, GCC/LTO] Fix PR69866: LTO with def for weak alias in regular object file
- Authentication-results: sourceware.org; auth=none
- References: <654b4277-ced9-e778-bcda-3054e1983727@foss.arm.com>
Ping?
Best regards,
Thomas
On 02/03/17 14:51, Thomas Preudhomme wrote:
Hi,
This patch fixes an assert failure when linking one LTOed object file
having a weak alias with a regular object file containing a strong
definition for that same symbol. The patch is twofold:
+ do not add an alias to a partition if it is external
+ do not declare (.globl) an alias if it is external
ChangeLog entries are as follow:
*** gcc/lto/ChangeLog ***
2017-03-01 Thomas Preud'homme <thomas.preudhomme@arm.com>
PR lto/69866
* lto/lto-partition.c (add_symbol_to_partition_1): Do not add external
aliases to partition.
*** gcc/ChangeLog ***
2017-03-01 Thomas Preud'homme <thomas.preudhomme@arm.com>
PR lto/69866
* cgraphunit.c (cgraph_node::assemble_thunks_and_aliases): Do not
declare external aliases.
*** gcc/testsuite/ChangeLog ***
2017-02-28 Thomas Preud'homme <thomas.preudhomme@arm.com>
PR lto/69866
* gcc.dg/lto/pr69866_0.c: New test.
* gcc.dg/lto/pr69866_1.c: Likewise.
Testing: Testsuite shows no regression when targeting Cortex-M3 with an
arm-none-eabi GCC cross-compiler, neither does it show any regression with
native LTO-bootstrapped x86-64_linux-gnu and aarch64-linux-gnu compilers.
Is this ok for stage4?
Best regards,
Thomas
diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
index c82a88a599ca61b068dd9783d2a6158163809b37..580500ff922b8546d33119261a2455235edbf16d 100644
--- a/gcc/cgraphunit.c
+++ b/gcc/cgraphunit.c
@@ -1972,7 +1972,7 @@ cgraph_node::assemble_thunks_and_aliases (void)
FOR_EACH_ALIAS (this, ref)
{
cgraph_node *alias = dyn_cast <cgraph_node *> (ref->referring);
- if (!alias->transparent_alias)
+ if (!alias->transparent_alias && !DECL_EXTERNAL (alias->decl))
{
bool saved_written = TREE_ASM_WRITTEN (decl);
diff --git a/gcc/lto/lto-partition.c b/gcc/lto/lto-partition.c
index e27d0d1690c1fcfb39e2fac03ce0f4154031fc7c..f44fd435ed075a27e373bdfdf0464eb06e1731ef 100644
--- a/gcc/lto/lto-partition.c
+++ b/gcc/lto/lto-partition.c
@@ -178,7 +178,8 @@ add_symbol_to_partition_1 (ltrans_partition part, symtab_node *node)
/* Add all aliases associated with the symbol. */
FOR_EACH_ALIAS (node, ref)
- if (!ref->referring->transparent_alias)
+ if (!ref->referring->transparent_alias
+ && ref->referring->get_partitioning_class () != SYMBOL_EXTERNAL)
add_symbol_to_partition_1 (part, ref->referring);
else
{
@@ -189,7 +190,8 @@ add_symbol_to_partition_1 (ltrans_partition part, symtab_node *node)
{
/* Nested transparent aliases are not permitted. */
gcc_checking_assert (!ref2->referring->transparent_alias);
- add_symbol_to_partition_1 (part, ref2->referring);
+ if (ref2->referring->get_partitioning_class () != SYMBOL_EXTERNAL)
+ add_symbol_to_partition_1 (part, ref2->referring);
}
}
diff --git a/gcc/testsuite/gcc.dg/lto/pr69866_0.c b/gcc/testsuite/gcc.dg/lto/pr69866_0.c
new file mode 100644
index 0000000000000000000000000000000000000000..f49ef8d4c1da7a21d1bfb5409d647bd18141595b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/pr69866_0.c
@@ -0,0 +1,13 @@
+/* { dg-lto-do link } */
+
+int _umh(int i)
+{
+ return i+1;
+}
+
+int weaks(int i) __attribute__((weak, alias("_umh")));
+
+int main()
+{
+ return weaks(10);
+}
diff --git a/gcc/testsuite/gcc.dg/lto/pr69866_1.c b/gcc/testsuite/gcc.dg/lto/pr69866_1.c
new file mode 100644
index 0000000000000000000000000000000000000000..3a14f850eefaffbf659ce4642adef7900330f4ed
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/lto/pr69866_1.c
@@ -0,0 +1,6 @@
+/* { dg-options { -fno-lto } } */
+
+int weaks(int i)
+{
+ return i+1;
+}