[ELF] Replace error() with errorOrWarn() for the ASSERT command

[MaskRay]

Summary

ld.bfd produces an output with --noinhibit-exec.
Use errorOrWarn() so that we can produce an output as well.

An interesting case is that symbol assignments may execute multiple
times, so we probably want to suppress errors for non-final runs.

[peter.smith]

LGTM. It can be useful to see an output file for debugging purposes. I agree it will be good to suppress multiple warnings but this could be done later.

lld/trunk/ELF/ScriptParser.cpp

Expr ScriptParser::readAssert() {
   expect("(");
   Expr e = readExpr();
   expect(",");
   StringRef msg = unquote(next());
   expect(")");
 
   return [=] {
     if (!e().getValue())
-      error(msg);
+      errorOrWarn(msg);
     return script->getDot();
   };
 }
 
 // Tries to read the special directive for an output section definition which
 // can be one of following: "(NOLOAD)", "(COPY)", "(INFO)" or "(OVERLAY)".
 // Tok1 and Tok2 are next 2 tokens peeked. See comment for readSectionAddressType below.
 bool ScriptParser::readSectionDirective(OutputSection *cmd, StringRef tok1, StringRef tok2) {

lld/trunk/test/ELF/linkerscript/assert.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.o
 
 # RUN: echo "SECTIONS { ASSERT(1, fail) }" > %t1.script
 # RUN: ld.lld -shared -o %t1 --script %t1.script %t1.o
 # RUN: llvm-readobj %t1 > /dev/null
 
 # RUN: echo "SECTIONS { ASSERT(0, fail) }" > %t3.script
-# RUN: not ld.lld -shared -o /dev/null --script %t3.script %t1.o > %t.log 2>&1
-# RUN: FileCheck %s -check-prefix=FAIL < %t.log
+# RUN: not ld.lld -o /dev/null -T %t3.script %t1.o 2>&1 | FileCheck --check-prefix=FAIL %s
+# RUN: ld.lld -o /dev/null -T %t3.script %t1.o --noinhibit-exec 2>&1 | FileCheck --check-prefix=FAIL %s
 # FAIL: fail
 
 # RUN: echo "SECTIONS { . = ASSERT(0x1000, fail); }" > %t4.script
 # RUN: ld.lld -shared -o %t4 --script %t4.script %t1.o
 # RUN: llvm-readobj %t4 > /dev/null
 
 # RUN: echo "SECTIONS { .foo : { *(.foo) } }" > %t5.script
 # RUN: echo "ASSERT(SIZEOF(.foo) == 8, fail);" >> %t5.script