[PATCH] D26801: Allow use define symbols to override linker defined ones

[Rafael Ávila de Espíndola via llvm-commits]

rafael created this revision.
rafael added a reviewer: ruiu.
rafael added a subscriber: llvm-commits.

I hit an internal linker script that was defining _DYNAMIC instead of letting the linker do it. It turns out that both bfd and gold allow that.

This is pretty easy to implement, just make the linker defined symbol weak. This should have no impact in the case where there is no user defined symbol: The visibility is hidden, which causes the output to still be local.


https://reviews.llvm.org/D26801

Files:
  ELF/Writer.cpp
  test/ELF/duplicate-internal.s
  test/ELF/linkerscript/dynamic-sym.s


Index: test/ELF/linkerscript/dynamic-sym.s
===================================================================
--- /dev/null
+++ test/ELF/linkerscript/dynamic-sym.s
@@ -0,0 +1,17 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: echo "_DYNAMIC = 0x123;" > %t.script
+# RUN: ld.lld -T %t.script %t.o -shared -o %t.so
+# RUN: llvm-readobj -t %t.so | FileCheck %s
+
+# CHECK:      Symbol {
+# CHECK:        Name: _DYNAMIC
+# CHECK-NEXT:   Value: 0x123
+# CHECK-NEXT:   Size: 0
+# CHECK-NEXT:   Binding: Local
+# CHECK-NEXT:   Type: None
+# CHECK-NEXT:   Other [
+# CHECK-NEXT:     STV_HIDDEN
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Section: Absolute
+# CHECK-NEXT: }
Index: test/ELF/duplicate-internal.s
===================================================================
--- test/ELF/duplicate-internal.s
+++ /dev/null
@@ -1,11 +0,0 @@
-# Should print an expected message in case of conflict with an internally generated symbol.
-
-# RUN: llvm-mc -filetype=obj -triple=mips-unknown-linux %s -o %t.o
-# RUN: not ld.lld -shared %t.o -o %t.so 2>&1 | FileCheck %s
-
-# CHECK: duplicate symbol '_gp' in {{.*}} and (internal)
-
-# REQUIRES: mips
-
-  .globl  _gp
-_gp = 0
Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -569,7 +569,7 @@
 static Symbol *addRegular(StringRef Name, InputSectionBase<ELFT> *IS,
                           typename ELFT::uint Value) {
   typename ELFT::Sym LocalHidden = {};
-  LocalHidden.setBindingAndType(STB_LOCAL, STT_NOTYPE);
+  LocalHidden.setBindingAndType(STB_WEAK, STT_NOTYPE);
   LocalHidden.setVisibility(STV_HIDDEN);
   LocalHidden.st_value = Value;
   return Symtab<ELFT>::X->addRegular(Name, LocalHidden, IS, nullptr);


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D26801.78367.patch
Type: text/x-patch
Size: 1777 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20161117/241b9ef4/attachment.bin>