Fix a Mach-O assembler segfault for a subtraction expression with an undefined symbol.

[oota-llvm.git] / lib / Target / X86 / MCTargetDesc / X86MachObjectWriter.cpp

diff --git a/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp b/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
index 8bfb7d5e3b37f3278138675cbc845a4ba7efb943..5685a7fde141b07510486d3c2ea574803a53f225 100644 (file)
--- a/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
+++ b/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
@@ -179,16 +179,19 @@ 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 == NULL ? 0 : Writer->getSymbolAddress(A_Base, Layout));
+      (!A_Base ? 0 : Writer->getSymbolAddress(A_Base, Layout));
     Value -= Writer->getSymbolAddress(&B_SD, Layout) -
-      (B_Base == NULL ? 0 : Writer->getSymbolAddress(B_Base, Layout));
+      (!B_Base ? 0 : Writer->getSymbolAddress(B_Base, Layout));
 
     if (A_Base) {
       Index = A_Base->getIndex();
@@ -231,7 +234,7 @@ void X86MachObjectWriter::RecordX86_64Relocation(MachObjectWriter *Writer,
       const MCSectionMachO &Section = static_cast<const MCSectionMachO&>(
         Fragment->getParent()->getSection());
       if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
-        Base = 0;
+        Base = nullptr;
     }
 
     // x86_64 almost always uses external relocations, except when there is no
@@ -525,7 +528,7 @@ void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer,
   }
 
   // Get the symbol data, if any.
-  const MCSymbolData *SD = 0;
+  const MCSymbolData *SD = nullptr;
   if (Target.getSymA())
     SD = &Asm.getSymbolData(Target.getSymA()->getSymbol());
 
@@ -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).