Not all files have gcno with bazel --coverage

Question

NB I have the custom targets which run by python scripts. So I couldn't use bazel coverage directly for this one.

1.

I defined in .bazelrc

build:coverage --collect_code_coverage
build:coverage --instrumentation_filter="^//src[/:]"
coverage --instrumentation_filter="^//src[/:]"

In the root BUILD

config_setting(
    name = "Coverage",
    flag_values = {
        ":coverage": "true",
    },
)

bool_flag(
    name = "coverage",
    build_setting_default = False,
)

In the cc_binary wrapper I use

+ select({"//:Coverage": coverageCopts, "//conditions:default": [], }),
// and 
select({"//:Coverage": coverageLopts, "//conditions:default": [], }),

where

coverageCopts = ["--coverage", "-fprofile-abs-path", "-fprofile-arcs", "-ftest-coverage"]
coverageLopts = ["--coverage", "-lgcov"]

and run this python script (from bazel) like this:

bazel run --subcommands --//\:coverage=true script:runner

But for some mystical reasons I have a lack of gcno files.
although there are these gcno's for neighboring files from the same library.
Grepping for bazel --subcommands indicates the presences of --coverage flag for this cpp file.
I did bazel clean --expunge - same result.

Which compiler/toolchain? Note that the --coverage compile and link flags should be enough - you likely do not ned the other -f... options. If you can find the subcommand used on a particular target: which directory did it run in, was the .o generated as you expected (is it instrumented?), and what happens if you run that command in your sandbox? — Henry Cox
– Henry Cox, Commented Aug 6 at 15:05
Yep, I started from simple --coverage flag. Toolchain is gcc. I found objcets file in the expected places. Not clearly understand about sandbox (is it bazel --sandbox_debug flag). — Ulrich Von Rekkenin
– Ulrich Von Rekkenin, Commented Aug 7 at 18:58
Sorry for the confusion. Merely asking what happens if you run the same compilation line with all the same environment variable settings - from your shell. Do you see an indentical .o, as you got from bzel, and is your .gcno generated? If so - then there is something unexpected in your bazel build flow. If not: then we can debug the compilation command line to figure out what is wrong. — Henry Cox
– Henry Cox, Commented Aug 11 at 14:21

Ulrich Von Rekkenin · Accepted Answer · 2025-08-11 11:52:05Z

0

Bazel option --collect_code_coverage solved this problem.

answered Aug 11 at 11:52

Ulrich Von Rekkenin

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1 Comment

Mark Schultheiss Aug 11 at 12:09

Perhaps improve this by incorporating this into the code presented as part of the answer to make this an even better answer here. Then accept the answer by clicking the check mark which self answering it perfectly acceptable to do.

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