[ELF] - Linkerscript: disallow discarding COMMON.

This patch restricts following construction:

/DISCARD/ : { *(COMMON) }

Previously LLD would crash.

Differential revision: https://reviews.llvm.org/D36468

llvm-svn: 310554
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 1fb787a..805d50b 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -319,8 +319,8 @@
 void LinkerScript::discard(ArrayRef<InputSectionBase *> V) {
   for (InputSectionBase *S : V) {
     S->Live = false;
-    if (S == InX::ShStrTab || S == InX::Dynamic || S == InX::DynSymTab ||
-        S == InX::DynStrTab)
+    if (S == InX::ShStrTab || S == InX::Common || S == InX::Dynamic ||
+        S == InX::DynSymTab || S == InX::DynStrTab)
       error("discarding " + S->Name + " section is not allowed");
     discard(S->DependentSections);
   }
diff --git a/lld/test/ELF/linkerscript/discard-section-err.s b/lld/test/ELF/linkerscript/discard-section-err.s
index 5d99555..8796843 100644
--- a/lld/test/ELF/linkerscript/discard-section-err.s
+++ b/lld/test/ELF/linkerscript/discard-section-err.s
@@ -21,3 +21,10 @@
 # RUN: not ld.lld -pie -o %t --script %t.script %t.o 2>&1 | \
 # RUN:   FileCheck -check-prefix=DYNSTR %s
 # DYNSTR: discarding .dynstr section is not allowed
+
+# RUN: echo "SECTIONS { /DISCARD/ : { *(COMMON) } }" > %t.script
+# RUN: not ld.lld -pie -o %t --script %t.script %t.o 2>&1 | \
+# RUN:   FileCheck -check-prefix=COMMON %s
+# COMMON: discarding COMMON section is not allowed
+
+.comm foo,4,4