[ELF] Update st_size when merging a common symbol with a shared symbol
When a common symbol is merged with a shared symbol, increase st_size if
the shared symbol has a larger st_size. At runtime, the executable's
symbol overrides the shared symbol. The shared symbol may be created
from common symbols in a previous link. This rule makes sure we pick
the largest size among all common symbols.
This behavior matches GNU ld. See
https://sourceware.org/bugzilla/show_bug.cgi?id=25236 for discussions.
A shared symbol does not hold alignment constraints. Ignore the
alignment update.
Reviewed By: peter.smith
Differential Revision: https://reviews.llvm.org/D71161
diff --git a/lld/ELF/Symbols.cpp b/lld/ELF/Symbols.cpp
index b5adbdc..f81e73e 100644
--- a/lld/ELF/Symbols.cpp
+++ b/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.
