[MC] Don't crash when trying to emit a relocation against .bss.

Turn that into an error instead.

llvm-svn: 276783

llvm/lib/MC/MCAssembler.cpp

@@ -575,8 +575,8 @@ void MCAssembler::writeSectionData(const MCSection *Sec,
         // into a virtual section. This is to support clients which use standard
         // directives to fill the contents of virtual sections.
         const MCDataFragment &DF = cast<MCDataFragment>(F);
-        assert(DF.fixup_begin() == DF.fixup_end() &&
-               "Cannot have fixups in virtual section!");
+        if (DF.fixup_begin() != DF.fixup_end())
+          report_fatal_error("cannot have fixups in virtual section!");
         for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
           if (DF.getContents()[i]) {
             if (auto *ELFSec = dyn_cast<const MCSectionELF>(Sec))

llvm/test/MC/X86/reloc-bss.s

@@ -0,0 +1,9 @@
+# RUN: not llvm-mc -filetype=obj -triple=x86_64-linux-gnu %s 2>&1 | FileCheck %s
+# CHECK: LLVM ERROR: cannot have fixups in virtual section!
+
+.section        .init_array,"awT",@nobits
+
+.hidden patatino
+.globl  patatino
+patatino:
+  movl __init_array_start, %eax