[llvm-objdump] Keep warning for --disassemble-functions in correct order.

[ychen]

Summary

relative to normal output when dumping archive files.

prepare for PR41911.

[MaskRay]

LG. A few nits below:

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

6 ↗

(On Diff #207910)

yaml2obj -o %t.o %s
rm -f %t.a
llvm-ar qc %t.a %t.o %t.o

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

384 ↗

(On Diff #207910)

Why was StringRef Prefix added? It does not seem to be used.

389 ↗

(On Diff #207910)

This is probably redundant. stderr is by default unbuffered. If the user makes it buffered, they should be prepared to see out-of-order output.

[jhenderson]

LGTM, with MaskRay's comments addressed.

[ychen]

• update

[ychen]

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

384 ↗

(On Diff #207910)

It was intended for the patch for PR35351. I've removed it.

389 ↗

(On Diff #207910)

Agree that it seems redundant but it makes explicit that stderr should be flushed there. Three other places in the same file use it too. I could remove them all or keep them all otherwise it is really confusing and inconsistent. Thoughts?

[ychen]

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

384 ↗

(On Diff #207910)

I meant to say PR41911.

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

 ## 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:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   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/trunk/tools/llvm-objdump/llvm-objdump.cpp

LLVM_ATTRIBUTE_NORETURN void error(Twine Message) {
   exit(1);
 }
 
 void warn(StringRef Message) {
   WithColor::warning(errs(), ToolName) << Message << ".\n";
   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) {
   WithColor::error(errs(), ToolName)
       << "'" << File << "': " << Message << ".\n";
   exit(1);
 }