[PATCH] D65584: [ELF] resolveUndefined: make STB_WEAK logic consistent for Undefined and SharedFile

[Fangrui Song via Phabricator via llvm-commits]

MaskRay updated this revision to Diff 212829.
MaskRay edited the summary of this revision.
MaskRay added a comment.

Mention --allow-shlib-undefined


Repository:
  rLLD LLVM Linker

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D65584/new/

https://reviews.llvm.org/D65584

Files:
  ELF/InputFiles.cpp
  ELF/Symbols.cpp
  ELF/Symbols.h
  test/ELF/weak-undef-shared.s


Index: test/ELF/weak-undef-shared.s
===================================================================
--- test/ELF/weak-undef-shared.s
+++ test/ELF/weak-undef-shared.s
@@ -30,6 +30,9 @@
 # RUN: ld.lld %t1.o %t2.so -o %t
 # RUN: llvm-readelf --dyn-syms %t | FileCheck --check-prefix=WEAK %s
 
+# RUN: ld.lld %t2.so %t1.o -o %t
+# RUN: llvm-readelf --dyn-syms %t | FileCheck --check-prefix=WEAK %s
+
 # WEAK:   NOTYPE WEAK   DEFAULT UND foo
 # GLOBAL: NOTYPE GLOBAL DEFAULT UND foo
 
Index: ELF/Symbols.h
===================================================================
--- ELF/Symbols.h
+++ ELF/Symbols.h
@@ -127,6 +127,11 @@
   // doesn't know the final contents of the symbol.
   unsigned canInline : 1;
 
+  // Used by Undefind and SharedSymbol to track if there has been at least one
+  // undefined reference to the symbol. The binding may change to STB_WEAK if
+  // the first undefined reference from a non-shared object is weak.
+  unsigned referenced : 1;
+
   // True if this symbol is specified by --trace-symbol option.
   unsigned traced : 1;
 
@@ -367,11 +372,6 @@
   uint64_t value; // st_value
   uint64_t size;  // st_size
   uint32_t alignment;
-
-  // This is true if there has been at least one undefined reference to the
-  // symbol. The binding may change to STB_WEAK if the first undefined reference
-  // is weak.
-  bool referenced = false;
 };
 
 // LazyArchive and LazyObject represent a symbols that is not yet in the link,
@@ -535,6 +535,7 @@
   isUsedInRegularObj = old.isUsedInRegularObj;
   exportDynamic = old.exportDynamic;
   canInline = old.canInline;
+  referenced = old.referenced;
   traced = old.traced;
   isPreemptible = old.isPreemptible;
   scriptDefined = old.scriptDefined;
Index: ELF/Symbols.cpp
===================================================================
--- ELF/Symbols.cpp
+++ ELF/Symbols.cpp
@@ -492,17 +492,13 @@
   if (dyn_cast_or_null<SharedFile>(other.file))
     return;
 
-  if (isUndefined()) {
-    // The binding may "upgrade" from weak to non-weak.
-    if (other.binding != STB_WEAK)
+  if (isUndefined() || isShared()) {
+    // The binding will be weak if there is at least one reference and all are
+    // weak. The binding has one opportunity to change to weak: if the first
+    // reference is weak.
+    if (other.binding != STB_WEAK || !referenced)
       binding = other.binding;
-  } else if (auto *s = dyn_cast<SharedSymbol>(this)) {
-    // The binding of a SharedSymbol will be weak if there is at least one
-    // reference and all are weak. The binding has one opportunity to change to
-    // weak: if the first reference is weak.
-    if (other.binding != STB_WEAK || !s->referenced)
-      binding = other.binding;
-    s->referenced = true;
+    referenced = true;
   }
 }
 
@@ -658,6 +654,6 @@
     uint8_t bind = binding;
     replace(other);
     binding = bind;
-    cast<SharedSymbol>(this)->referenced = true;
+    referenced = true;
   }
 }
Index: ELF/InputFiles.cpp
===================================================================
--- ELF/InputFiles.cpp
+++ ELF/InputFiles.cpp
@@ -1098,6 +1098,7 @@
     // Handle global undefined symbols.
     if (eSym.st_shndx == SHN_UNDEF) {
       this->symbols[i]->resolve(Undefined{this, name, binding, stOther, type});
+      this->symbols[i]->referenced = true;
       continue;
     }
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D65584.212829.patch
Type: text/x-patch
Size: 3337 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190801/a9024fd1/attachment.bin>