[ELF] for symver directives, preserve the given symbol's size

[aeden]

Summary

A versioned symbol alias created by .symver should copy the size from the source symbol, since it may be used by R_X86_64_COPY and the like.

[MaskRay]

Can you add a test to test/MC/ELF/symver.s?
I can add one and commit it on your behalf if you don't have commit access

[aeden]

Updated to include llvm/test/MC/ELF/symver.s modifications

[MaskRay]

llvm/test/MC/ELF/symver.s

26

You can set the size of global1 instead of adding a new symbol

[aeden]

Updated to use existing global1 in llvm/test/MC/ELF/symver.s

[MaskRay]

LGTM.

[aeden]

Ping. Would love to see this in an upcoming release.

[MaskRay]

I think st_size is already correct. Please see line 544 if (!ESize && Base) ESize = Base->getSize();

llvm/lib/MC/ELFObjectWriter.cpp

for (const std::pair<StringRef, const MCSymbol *> &P : Asm.Symvers) {
     const MCExpr *Value = MCSymbolRefExpr::create(&Symbol, Asm.getContext());
     Alias->setVariableValue(Value);
 
     // Aliases defined with .symvar copy the binding from the symbol they alias.
     // This is the first place we are able to copy this information.
     Alias->setExternal(Symbol.isExternal());
     Alias->setBinding(Symbol.getBinding());
     Alias->setOther(Symbol.getOther());
+    Alias->setSize(Symbol.getSize());
 
     if (!Symbol.isUndefined() && !Rest.startswith("@@@"))
       continue;
 
     // FIXME: Get source locations for these errors or diagnose them earlier.
     if (Symbol.isUndefined() && Rest.startswith("@@") &&
         !Rest.startswith("@@@")) {
       Asm.getContext().reportError(SMLoc(), "versioned symbol " + AliasName +

llvm/test/MC/ELF/symver.s

defined3:
 
         .long defined1
         .long undefined1
         .long defined2
         .long defined3
         .long undefined3
 
         .global global1
+        .type   global1, @object
+        .size   global1, 4
         .symver global1, g1@@zed
 global1:
 
+
 // CHECK:      Relocations [
 // CHECK-NEXT:   Section {{.*}} .rela.text {
 // CHECK-NEXT:     0x0 R_X86_64_32 .text 0x0
 // CHECK-NEXT:     0x4 R_X86_64_32 bar2@zed 0x0
 // CHECK-NEXT:     0x8 R_X86_64_32 .text 0x0
 // CHECK-NEXT:     0xC R_X86_64_32 .text 0x0
 // CHECK-NEXT:     0x10 R_X86_64_32 bar6@zed 0x0
 // CHECK-NEXT:   }

 // CHECK-NEXT:     Binding: Global
 // CHECK-NEXT:     Type: None
 // CHECK-NEXT:     Other: 0
 // CHECK-NEXT:     Section: Undefined
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Symbol {
 // CHECK-NEXT:     Name: g1@@zed
 // CHECK-NEXT:     Value: 0x14
-// CHECK-NEXT:     Size: 0
+// CHECK-NEXT:     Size: 4
 // CHECK-NEXT:     Binding: Global
-// CHECK-NEXT:     Type: None
+// CHECK-NEXT:     Type: Object
 // CHECK-NEXT:     Other: 0
 // CHECK-NEXT:     Section: .text
 // CHECK-NEXT:   }
 // CHECK-NEXT:   Symbol {
 // CHECK-NEXT:     Name: global1
 // CHECK-NEXT:     Value: 0x14
-// CHECK-NEXT:     Size: 0
+// CHECK-NEXT:     Size: 4
 // CHECK-NEXT:     Binding: Global
-// CHECK-NEXT:     Type: None
+// CHECK-NEXT:     Type: Object
 // CHECK-NEXT:     Other: 0
 // CHECK-NEXT:     Section: .text
 // CHECK-NEXT:   }
 // CHECK-NEXT: ]