Fix ARM __cxa_end_cleanup() and gc-sections.

loganchien · loganchien · commit 338d6de5fa4a · 2015-12-22T14:38:30.000Z
This commit adds SHF_ALLOC and SHF_EXECINSTR section flags to `.text.__cxa_end_cleanup` section. This fixes a link error when we are using integrated-as and `ld.gold` (with `-Wl,--gc-sections` and `-Wl,--fatal-warnings`.) Detailed Explanation: 1. There might be some problem with LLVM integrated-as. It is not emitting any section flags for text sections. (This will be fixed in an independent commit.) 2. `ld.gold` will skip the external symbols in the section without SHF_ALLOC. This is the reason why `.text.__cxa_end_cleanup_impl` section is discarded even though it is referenced by `__cxa_end_cleanup()`. This commit workaround the problem by specifying the section flags explicitly. Fix http://llvm.org/PR21292 llvm-svn: 256241
diff --git a/libcxxabi/src/cxa_exception.cpp b/libcxxabi/src/cxa_exception.cpp
@@ -334,7 +334,7 @@ __cxa_end_cleanup_impl()
 }
 
 asm (
-    "	.pushsection	.text.__cxa_end_cleanup\n"
+    "	.pushsection	.text.__cxa_end_cleanup,\"ax\",%progbits\n"
     "	.globl	__cxa_end_cleanup\n"
     "	.type	__cxa_end_cleanup,%function\n"
     "__cxa_end_cleanup:\n"

Original file line number	Diff line number	Diff line change
`@@ -334,7 +334,7 @@ __cxa_end_cleanup_impl()`
`334`	`334`	`}`
`335`	`335`
`336`	`336`	`asm (`
`337`		`- " .pushsection .text.__cxa_end_cleanup\n"`
	`337`	`+ " .pushsection .text.__cxa_end_cleanup,\"ax\",%progbits\n"`
`338`	`338`	`" .globl __cxa_end_cleanup\n"`
`339`	`339`	`" .type __cxa_end_cleanup,%function\n"`
`340`	`340`	`"__cxa_end_cleanup:\n"`