1 files changed, 8 insertions, 5 deletions
diff --git a/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp b/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
index ead3338..5685a7f 100644
--- a/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
+++ b/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
@@ -179,11 +179,14 @@ void X86MachObjectWriter::RecordX86_64Relocation(MachObjectWriter *Writer,
     if (A_Base == B_Base && A_Base)
       report_fatal_error("unsupported relocation with identical base", false);
 
-    // A subtraction expression where both symbols are undefined is a
+    // A subtraction expression where either symbol is undefined is a
     // non-relocatable expression.
-    if (A->isUndefined() && B->isUndefined())
-      report_fatal_error("unsupported relocation with subtraction expression",
-                         false);
+    if (A->isUndefined() || B->isUndefined()) {
+      StringRef Name = A->isUndefined() ? A->getName() : B->getName();
+      Asm.getContext().FatalError(Fixup.getLoc(),
+        "unsupported relocation with subtraction expression, symbol '" + 
+        Name + "' can not be undefined in a subtraction expression");
+    }
 
     Value += Writer->getSymbolAddress(&A_SD, Layout) -
       (!A_Base ? 0 : Writer->getSymbolAddress(A_Base, Layout));
@@ -572,7 +575,7 @@ void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer,
       // For external relocations, make sure to offset the fixup value to
       // compensate for the addend of the symbol address, if it was
       // undefined. This occurs with weak definitions, for example.
-      if (!SD->Symbol->isUndefined())
+      if (!SD->getSymbol().isUndefined())
         FixedValue -= Layout.getSymbolOffset(SD);
     } else {
       // The index is the section ordinal (1-based).