[PATCH] D71161: [ELF] Update st_size when merging a common symbol with a shared symbol
Fangrui Song via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Fri Dec 13 09:29:06 PST 2019
This revision was automatically updated to reflect the committed changes.
Closed by commit rG69d10d282e58: [ELF] Update st_size when merging a common symbol with a shared symbol (authored by MaskRay).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D71161/new/
https://reviews.llvm.org/D71161
Files:
lld/ELF/Symbols.cpp
lld/test/ELF/common-shared.s
Index: lld/test/ELF/common-shared.s
===================================================================
--- /dev/null
+++ lld/test/ELF/common-shared.s
@@ -0,0 +1,16 @@
+# REQUIRES: x86
+## When a common symbol is merged with a shared symbol, pick the larger st_size.
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
+# RUN: echo '.globl com; .comm com, 16' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
+# RUN: ld.lld -shared %t1.o -o %t1.so
+
+# RUN: ld.lld %t.o %t1.so -o %t
+# RUN: llvm-readelf -s %t | FileCheck %s
+# RUN: ld.lld %t1.so %t.o -o %t
+# RUN: llvm-readelf -s %t | FileCheck %s
+
+# CHECK: 16 OBJECT GLOBAL DEFAULT 7 com
+
+.globl com
+.comm com,1
Index: lld/ELF/Symbols.cpp
===================================================================
--- lld/ELF/Symbols.cpp
+++ lld/ELF/Symbols.cpp
@@ -620,7 +620,18 @@
return;
if (cmp > 0) {
- replace(other);
+ if (auto *s = dyn_cast<SharedSymbol>(this)) {
+ // Increase st_size if the shared symbol has a larger st_size. The shared
+ // symbol may be created from common symbols. The fact that some object
+ // files were linked into a shared object first should not change the
+ // regular rule that picks the largest st_size.
+ uint64_t size = s->size;
+ replace(other);
+ if (size > cast<CommonSymbol>(this)->size)
+ cast<CommonSymbol>(this)->size = size;
+ } else {
+ replace(other);
+ }
return;
}
@@ -661,6 +672,12 @@
}
void Symbol::resolveShared(const SharedSymbol &other) {
+ if (isCommon()) {
+ // See the comment in resolveCommon() above.
+ if (other.size > cast<CommonSymbol>(this)->size)
+ cast<CommonSymbol>(this)->size = other.size;
+ return;
+ }
if (visibility == STV_DEFAULT && (isUndefined() || isLazy())) {
// An undefined symbol with non default visibility must be satisfied
// in the same DSO.
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