[llvm-objcopy] - Report "no zlib available" error properly when --compress-debug-sections is used.

[grimar]

Summary

If zlib is not available, and --compress-debug-sections is passed,
we want to report an error. Currently, it is only reported for
--compress_debug_sections= form of the option.

Fixes the https://bugs.llvm.org/show_bug.cgi?id=40886.

I do not think there is a way to write a test for this.

[jhenderson]

This is for llvm-objcopy, not llvm-objdump as claimed in the header and description, right?

Can you write a test that is UNSUPPORTED if zlib IS available?

[grimar]

In D58909#1417023, @jhenderson wrote:

Can you write a test that is UNSUPPORTED if zlib IS available?

I think we have such a test already. It is:
https://github.com/llvm-mirror/llvm/blob/master/test/tools/llvm-objcopy/ELF/compress-debug-sections-invalid-format.test
(It does not do # REQUIRES: zlib because code report the Invalid or unsupported --compress-debug-sections format error before zlib::isAvailable() check.
What looks fine to me.)

[jhenderson]

In D58909#1418084, @grimar wrote:

In D58909#1417023, @jhenderson wrote:

Can you write a test that is UNSUPPORTED if zlib IS available?

I think we have such a test already. It is:
https://github.com/llvm-mirror/llvm/blob/master/test/tools/llvm-objcopy/ELF/compress-debug-sections-invalid-format.test
(It does not do # REQUIRES: zlib because code report the Invalid or unsupported --compress-debug-sections format error before zlib::isAvailable() check.
What looks fine to me.)

That isn't the same test as I meant. That checks the error message at line 475, whereas I'm looking for a test for line 483. In other words, a valid compression format, but where zlib::isAvailable fails. It may not be possible of course.

[grimar]

In D58909#1418102, @jhenderson wrote:

In D58909#1418084, @grimar wrote:

In D58909#1417023, @jhenderson wrote:

Can you write a test that is UNSUPPORTED if zlib IS available?

I think we have such a test already. It is:
https://github.com/llvm-mirror/llvm/blob/master/test/tools/llvm-objcopy/ELF/compress-debug-sections-invalid-format.test
(It does not do # REQUIRES: zlib because code report the Invalid or unsupported --compress-debug-sections format error before zlib::isAvailable() check.
What looks fine to me.)

That isn't the same test as I meant. That checks the error message at line 475, whereas I'm looking for a test for line 483. In other words, a valid compression format, but where zlib::isAvailable fails. It may not be possible of course.

Yes, as I mentioned in the description I do not think it is possible. FWIW in LLD we do not check this error either.

[jhenderson]

Okay, LGTM. I just verified that it works locally, when it didn't before.

By the way, is this fixing https://bugs.llvm.org/show_bug.cgi?id=40886? I think it does for me.

[grimar]

In D58909#1418115, @jhenderson wrote:

By the way, is this fixing https://bugs.llvm.org/show_bug.cgi?id=40886? I think it does for me.

Yes, I think so too. Since now it will emit an error saying zlib isn't available.
In the description of this patch, I wrote "sections silently remain uncompressed in the output" but I just rechecked it
and they are stripped out for me too. Perhaps I looked at the wrong console window, I am not sure. I'll fix the description.

My reason to fix it was that I couldn't reproduce an error reported in https://bugs.llvm.org/show_bug.cgi?id=40885 on windows (with zlib off).

[jhenderson]

In D58909#1418126, @grimar wrote:

My reason to fix it was that I couldn't reproduce an error reported in https://bugs.llvm.org/show_bug.cgi?id=40885 on windows (with zlib off).

Yes, that's how I discovered the bug this fixes actually! I just didn't have time to dig into it and fix it, so thanks. BTW, you'll definitely need zlib in order to reproduce https://bugs.llvm.org/show_bug.cgi?id=40885.

llvm/trunk/tools/llvm-objcopy/CopyConfig.cpp

if (Arg->getOption().getID() == OBJCOPY_compress_debug_sections_eq) {
               .Default(DebugCompressionType::None);
       if (Config.CompressionType == DebugCompressionType::None)
         return createStringError(
             errc::invalid_argument,
             "Invalid or unsupported --compress-debug-sections format: %s",
             InputArgs.getLastArgValue(OBJCOPY_compress_debug_sections_eq)
                 .str()
                 .c_str());
-      if (!zlib::isAvailable())
-        return createStringError(
-            errc::invalid_argument,
-            "LLVM was not compiled with LLVM_ENABLE_ZLIB: can not compress");
-    }
-  }
+    }
 
   Config.AddGnuDebugLink = InputArgs.getLastArgValue(OBJCOPY_add_gnu_debuglink);
   Config.BuildIdLinkDir = InputArgs.getLastArgValue(OBJCOPY_build_id_link_dir);
   if (InputArgs.hasArg(OBJCOPY_build_id_link_input))
     Config.BuildIdLinkInput =
         InputArgs.getLastArgValue(OBJCOPY_build_id_link_input);
   if (InputArgs.hasArg(OBJCOPY_build_id_link_output))
     Config.BuildIdLinkOutput =