[llvm-objdump] Keep warning for --disassemble-functions in correct or…

…der.

relative to normal output when dumping archive files.

prepare for PR35351.

Reviewers: jhenderson, grimar, MaskRay, rupprecht

Reviewed by: MaskRay, jhenderson

Differential Revision: https://reviews.llvm.org/D64165

llvm-svn: 365564

llvm/test/tools/llvm-objdump/X86/warn-missing-disasm-func.test

@@ -1,5 +1,10 @@
 ## Warn if --disassemble-functions specifies an unknown symbol.
-# RUN: yaml2obj %s | llvm-objdump - --disassemble-functions=foo 2>&1 | FileCheck %s
+
+# RUN: yaml2obj -o %t.o %s
+# RUN: rm -f %t.a
+# RUN: llvm-ar qc %t.a %t.o %t.o
+# RUN: llvm-objdump --disassemble-functions=foo %t.o 2>&1 | FileCheck %s
+# RUN: llvm-objdump --disassemble-functions=foo %t.a 2>&1 | FileCheck %s --check-prefix=MULTI
 
 --- !ELF
 FileHeader:
@@ -9,3 +14,8 @@ FileHeader:
   Machine: EM_X86_64
 
 # CHECK: warning: failed to disassemble missing function foo
+
+# MULTI: file format ELF64-x86-64
+# MULTI: warning: failed to disassemble missing function foo
+# MULTI: file format ELF64-x86-64
+# MULTI: warning: failed to disassemble missing function foo

llvm/tools/llvm-objdump/llvm-objdump.cpp

@@ -386,8 +386,12 @@ void warn(StringRef Message) {
   errs().flush();
 }
 
-void warn(Twine Message) {
+static void warn(Twine Message) {
+  // Output order between errs() and outs() matters especially for archive
+  // files where the output is per member object.
+  outs().flush();
   WithColor::warning(errs(), ToolName) << Message << "\n";
+  errs().flush();
 }
 
 LLVM_ATTRIBUTE_NORETURN void report_error(StringRef File, Twine Message) {