Why doesn't gcov report any lines being covered by my unit tests?

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+12 Q:

Why doesn't gcov report any lines being covered by my unit tests?

I am using Xcode 3.2 on 10.6, with the shipped version of gcov and default GCC compiler (both version 4.2.1). I have created a dependent Cocoa unit test bundle which is injected into my app, and followed Apple's documentation on setting up a gcov-instrumented build configuration - based on the Debug configuration which doesn't have any compiler optimisations enabled.

When I build the test bundle with this 'Gcov-instrumented' configuration, the app launches and the tests are injected and run. Also the coverage statistics files are generated at:

build/<AppTarget>.build/Gcov-instrumented/<AppTarget>.build/Objects-normal/x86_64/<object>.gcda

build/<AppTarget>.build/Gcov-instrumented/<AppTarget>.build/Objects-normal/x86_64/<object>.gcno

So far so good. I know the tests are really being run because if I insert failures then the test suite fails as expected. Unfortunately, gcov reports that no lines of the objects have been covered by the tests! Every line is reported as 0 coverage. I've searched here and at the Apple mailing list archives, and can't find anyone with a similar problem. I expect I'm missing something - but what is it?

+10 A:

I have been running into this problem intermittently. I stumbled into a good length of lucky time where it was "mostly working" in my main project. By mostly working I mean I was able to get coverage to show up, but with a little more pain than on 10.5. I had to aggressively delete the coverage files and rebuild in order to get any updates, for instance. Even in my "barely working" state, the compiler/runtime doesn't seem willing to overwrite an existing coverage data file.

I think I've stumbled back on to a working scenario. Voodoo for sure, and less than ideal:

Make sure the SDK is 10.6.
Make sure the deployment is set to gcc 4.0 (!).
Do a full clean of the project.
Rebuild.

Does this get you the expected coverage data?

Granted, I would expect to be able to generate coverage files that work using gcc 4.2 or one of the LLVM compilers, but for the moment this seems to have me slightly less crippled than before.

Another clue: when I observe the coverage data (using Google's Cover Story), I get warnings like:

/BUILDRESULTS/MarsEdit.build/Code Coverage/MarsEditDataModelTests.build/Objects-normal/i386/MEDataItem.gcno:version '400A', prefer '402*'

But the coverage information is still presented. So it seems it's balking at an older coverage format version, but if I use the newer compiler (4.2) which would presumably generate the newer format .gcno files, the 0% coverage problem plagues me as it does Graham.

danielpunkass 2009-10-12 17:10:19

Thanks for that! I now do get the coverage I'd expect :-)

Graham Lee 2009-10-13 08:25:07

+1 I got it working with the same approach on Snow Leopard. The requirement to drop to GCC 4.0 is somewhat disconcerting going forward, since code that must be compiled with GCC 4.2 or LLVM (for example, if it uses Blocks) won't work in the old compiler version, and code coverage may disappear. This sounds like a Radar waiting to be filed...

Quinn Taylor 2010-02-24 20:49:07

Daniel, I run into similar problems when using lcov to generate HTML coverage reports. It allows me to pass `--gcov-tool /usr/bin/gcov-4.0` to override the default of 4.2, which `/usr/bin/gcov` points to. I peeked at the source of CoverStory, and it's using this symlink. http://code.google.com/p/coverstory/source/browse/trunk/CoverStoryDocument.m#131 Sure would be nice if they **did** add a user default for this, even if it's not in the preferences dialog...

Quinn Taylor 2010-02-25 22:06:12

Quinn, where do you enter the `--gcov-tool /usr/bin/gcov-4.0` flags? I've tried this in the linker flags setting, but when I compile, Xcode throws an error at me. When I try to do a gcc compile from the command line with this flag, it also throws an error: `ld: warning: in /usr/bin/gcov-4.0, missing required architecture x86_64 in file`

John Gallagher 2010-04-04 15:09:18

@danielpunkass Or I did, until I started using blocks and couldn't use GCC 4.0 :(

Graham Lee 2010-06-13 10:09:02

You can get code coverage working with gcc 4.2.1. Details here:

SnowLeopardGCov

dmaclach 2010-06-01 22:25:15

The contents of that page have been replaced (as of June 4th) with the message “This page is out of date. This information has been consolidated into the Google Toolbox For Mac Wiki.” and a link to http://code.google.com/p/google-toolbox-for-mac/wiki/SnowLeopardGCov .

Peter Hosey 2010-06-07 00:47:55

Fixed up with the new improved link. Thanks Peter.

dmaclach 2010-06-07 16:20:48

@dmaclach, that didn't work for me. I set the compiler to 4.2, removed the prefix headers and did an entirely clean build of the unit test target. I don't get any coverage information at all.

Graham Lee 2010-06-13 10:08:32

Hey Graham. I assume you also turned on the "Instrument Program Flow" and "Generate Test Coverage Files" flags for the target?

dmaclach 2010-06-15 03:47:56

ansaurus

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Why doesn't gcov report any lines being covered by my unit tests?

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