Bug 15658 - Support building glibc with -flto.
Summary: Support building glibc with -flto.
Status: NEW
Alias: None
Product: glibc
Classification: Unclassified
Component: build (show other bugs)
Version: 2.18
: P2 enhancement
Target Milestone: ---
Assignee: Not yet assigned to anyone
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2013-06-20 12:56 UTC by Carlos O'Donell
Modified: 2024-03-15 09:31 UTC (History)
2 users (show)

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Last reconfirmed:
fweimer: security-

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Description Carlos O'Donell 2013-06-20 12:56:58 UTC 
You can't build glibc with -flto.

glibc master is currently unbuildable with -flto because of:
http://sourceware.org/bugzilla/show_bug.cgi?id=15648

You should always see:
checking for .preinit_array/.init_array/.fini_array support... no
configure: error: Need linker with .init_array/.fini_array support.

This is because -flto throws out the .init_array support.

A potential fix is:
diff --git a/configure.in b/configure.in
index 8b11081..415e777 100644
--- a/configure.in
+++ b/configure.in
@@ -1383,7 +1383,7 @@ AC_CACHE_CHECK(for .preinit_array/.init_array/.fini_array support,
               libc_cv_initfini_array, [dnl
 LIBC_TRY_LINK_STATIC([
 int foo (void) { return 1; }
-int (*fp) (void) __attribute__ ((section (".init_array"))) = foo;
+int (*fp) (void) __attribute__ ((section (".init_array"), used)) = foo;
 ],
   [if $READELF -S conftest | fgrep INIT_ARRAY > /dev/null; then
     libc_cv_initfini_array=yes
~~~

However, given that nobody has built with -flto it's going to require considerable work to make it happen.

This is an enhancement.