Fixed a crash in llvm-mc for Mach-O when a symbol difference expressi…

…on uses a

symbol from an assignment.  In this case the symbol did not have a fragment so
MCObjectWriter::IsSymbolRefDifferenceFullyResolved() should not have been
calling IsSymbolRefDifferenceFullyResolvedImpl() with a NULL fragment and should
just have returned false in that case.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149442 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/MCObjectWriter.cpp

@@ -68,6 +68,8 @@ MCObjectWriter::IsSymbolRefDifferenceFullyResolved(const MCAssembler &Asm,
 
   const MCSymbolData &DataA = Asm.getSymbolData(SA);
   const MCSymbolData &DataB = Asm.getSymbolData(SB);
+  if(!DataA.getFragment() || !DataB.getFragment())
+    return false;
 
   return IsSymbolRefDifferenceFullyResolvedImpl(Asm, DataA,
                                                 *DataB.getFragment(),

test/MC/MachO/darwin-x86_64-diff-reloc-assign.s

@@ -0,0 +1,27 @@
+// RUN: llvm-mc -triple x86_64-apple-darwin9 %s -filetype=obj -o - | macho-dump --dump-section-data | FileCheck %s
+
+// Test case for rdar://10743265
+
+// This tests that this expression does not cause a crash and produces two
+// relocation entries:
+// Relocation information (__TEXT,__text) 2 entries
+// address  pcrel length extern type    scattered symbolnum/value
+// 00000000 False long   True   SUB     False     _base
+// 00000000 False long   True   UNSIGND False     _start_ap_2
+
+_base = .
+
+.long (0x2000) + _start_ap_2 - _base 
+.word 0
+
+_start_ap_2:
+        cli
+
+// CHECK:   ('_relocations', [
+// CHECK:     # Relocation 0
+// CHECK:     (('word-0', 0x0),
+// CHECK:      ('word-1', 0x5c000000)),
+// CHECK:     # Relocation 1
+// CHECK:     (('word-0', 0x0),
+// CHECK:      ('word-1', 0xc000001)),
+// CHECK:   ])