Libgcov profiling error

#include<stdio.h>
void fun1();
int main(){
    fun1();
}

#include<stdio.h>
void fun2();
int main(){
    fun2();
}

void fun1(){
        printf("fun1n");
}

void fun2(){
        printf("fun2n");
}

gcc -Wall -fprofile-arcs -ftest-coverage ut1.c common.c -o ut1
gcc -Wall -fprofile-arcs -ftest-coverage ut2.c common.c -o ut2

./ut1
./ut2

    -:    0:Source:common.c
    -:    0:Graph:common.gcno
    -:    0:Data:common.gcda
    -:    0:Runs:1
    -:    0:Programs:1
    -:    1:void fun1(){
    -:    2:        printf("fun1n");
    -:    3:}
    -:    4:
    1:    5:void fun2(){
    1:    6:        printf("fun2n");
    1:    7:}

2 ответа

Лучший ответ

$ ./ut1
fun1
$ ./ut2
fun2
libgcov profiling error:/tmp/gcov-test/common.gcda:overwriting an existing profile data with a different timestamp

# compile common.c
gcc -Wall --coverage -c common.c -o common.o

# compile ut1 and ut2, and link with common.o
gcc -Wall --coverage ut1.c common.o -o ut1
gcc -Wall --coverage ut2.c common.o -o ut2

        -:    0:Source:common.c
        -:    0:Graph:common.gcno
        -:    0:Data:common.gcda
        -:    0:Runs:2
        -:    1:#include<stdio.h>
        1:    2:void fun1(){
        1:    3:        printf("fun1n");
        1:    4:}
        -:    5:
        1:    6:void fun2(){
        1:    7:        printf("fun2n");
        1:    8:}

lcov --capture --rc lcov_branch_coverage=1 --directory dir_1 --config-file ./lcovrc --output coverage_1.info
lcov --capture --rc lcov_branch_coverage=1 --directory dir_2 --config-file ./lcovrc --output coverage_2.info

genhtml --branch-coverage --output ./generated-coverage/ merged_coverage.info

Comments

Found that 'actions/checkout' does not remove all temporary files from
previous runs in submodules [1], it runs only 'git clean --xffd' [2]:

  libgcov profiling error:/home/ubuntu/actions-runner/_work/tarantool/tarantool/src/lib/small/CMakeFiles/small.dir/small/small_class.c.gcda:overwriting an existing profile data with a different timestamp

To avoid of it added:

  git submodules foreach --recursive 'git clean -xffd'

to 'actions/environment' which is run after each 'actions/checkout'.

Part of #5986

[1]: https://github.com/tarantool/tarantool/runs/2318244478?check_suite_focus=true#step:5:4012
[2]: actions/checkout#358

Found that 'actions/checkout' does not remove all temporary files from
previous runs in submodules [1], it runs only 'git clean --xffd' [2]:

  libgcov profiling error:/home/ubuntu/actions-runner/_work/tarantool/tarantool/src/lib/small/CMakeFiles/small.dir/small/small_class.c.gcda:overwriting an existing profile data with a different timestamp

To avoid of it added:

  git submodules foreach --recursive 'git clean -xffd'

to 'actions/environment' which is run after each 'actions/checkout'.

Part of #5986

[1]: https://github.com/tarantool/tarantool/runs/2318244478?check_suite_focus=true#step:5:4012
[2]: actions/checkout#358

Found that 'actions/checkout' does not remove all temporary files from
previous runs in submodules [1], it runs only 'git clean --xffd' [2]:

  libgcov profiling error:/home/ubuntu/actions-runner/_work/tarantool/tarantool/src/lib/small/CMakeFiles/small.dir/small/small_class.c.gcda:overwriting an existing profile data with a different timestamp

To avoid of it added:

  git submodules foreach --recursive 'git clean -xffd'

to 'actions/environment' which is run after each 'actions/checkout'.

Part of #5986

[1]: https://github.com/tarantool/tarantool/runs/2318244478?check_suite_focus=true#step:5:4012
[2]: actions/checkout#358

Found that 'actions/checkout' does not remove all temporary files from
previous runs in submodules [1], it runs only 'git clean --xffd' [2]:

  libgcov profiling error:/home/ubuntu/actions-runner/_work/tarantool/tarantool/src/lib/small/CMakeFiles/small.dir/small/small_class.c.gcda:overwriting an existing profile data with a different timestamp

To avoid of it added:

  git submodules foreach --recursive 'git clean -xffd'

to 'actions/environment' which is run after each 'actions/checkout'.

Part of #5986

[1]: https://github.com/tarantool/tarantool/runs/2318244478?check_suite_focus=true#step:5:4012
[2]: actions/checkout#358

(cherry picked from commit 57ab8c2)

Found that 'actions/checkout' does not remove all temporary files from
previous runs in submodules [1], it runs only 'git clean --xffd' [2]:

  libgcov profiling error:/home/ubuntu/actions-runner/_work/tarantool/tarantool/src/lib/small/CMakeFiles/small.dir/small/small_class.c.gcda:overwriting an existing profile data with a different timestamp

To avoid of it added:

  git submodules foreach --recursive 'git clean -xffd'

to 'actions/environment' which is run after each 'actions/checkout'.

Part of #5986

[1]: https://github.com/tarantool/tarantool/runs/2318244478?check_suite_focus=true#step:5:4012
[2]: actions/checkout#358

(cherry picked from commit 57ab8c2)

Found that 'actions/checkout' does not remove all temporary files from
previous runs in submodules [1], it runs only 'git clean --xffd' [2]:

  libgcov profiling error:/home/ubuntu/actions-runner/_work/tarantool/tarantool/src/lib/small/CMakeFiles/small.dir/small/small_class.c.gcda:overwriting an existing profile data with a different timestamp

To avoid of it added:

  git submodules foreach --recursive 'git clean -xffd'

to 'actions/environment' which is run after each 'actions/checkout'.

Part of #5986

[1]: https://github.com/tarantool/tarantool/runs/2318244478?check_suite_focus=true#step:5:4012
[2]: actions/checkout#358

(cherry picked from commit 57ab8c2)

При сборке программы с включенными опциями для GCOV можно получить ошибку на этапе линковки следующего вида:

/usr/bin/ld: ./a.out: hidden symbol `__gcov_merge_add’ in /usr/lib/gcc/i486-linux-gnu/4.1.3/libgcov.a(_gcov_merge_add.o) is referenced by DSO
/usr/bin/ld: final link failed: Nonrepresentable section on output

Скорее всего причина заключается в том, что к исполняемому модулю линкуются библиотеки, которые тоже были скомпилированы с опциями -fprofile-arcs -ftest-coverage.

Простой пример, иллюстрирующий проблему.

Даны два файла:

=== a.cpp
#include <stdio.h>

Из файла b.cpp делаем статическую библиотеку libmy.a, а из файла a.cpp — исполняемый модуль a.out:

g++ -c -fprofile-arcs -ftest-coverage b.cpp
g++ -shared -o libmy.a ./b.o
g++ -c -fprofile-arcs -ftest-coverage a.cpp
g++ -o a.out a.o -L. -lmy


Получаем ошибку вида «undefined reference to `__gcov_init’» — забыли подключить библиотеку libgcov.a.

Подключаем к сборке требуемую библиотеку как обычно:

g++ -c -fprofile-arcs -ftest-coverage b.cpp
g++ -shared -o libmy.a ./b.o
g++ -c -fprofile-arcs -ftest-coverage a.cpp
g++ -o a.out a.o -L. -lmy -lgcov


Вот здесь-то и получаем странную ошибку:

/usr/bin/ld: ./a.out: hidden symbol `__gcov_merge_add' in /usr/lib/gcc/i486-linux-gnu/4.1.3/libgcov.a(_gcov_merge_add.o) is referenced by DSO
/usr/bin/ld: final link failed: Nonrepresentable section on output


Исправить это просто. Нужно подключить библиотеку libgcov.a не только к сборке исполняемого модуля, но и к сборке статической библиотеки:

g++ -c -fprofile-arcs -ftest-coverage b.cpp
g++ -shared -o libmy.a ./b.o -lgcov
g++ -c -fprofile-arcs -ftest-coverage a.cpp
g++ -o a.out a.o -L. -lmy -lgcov


Вот и всё. Так нужно поступить с каждой библиотекой, исходный код которой скомпилирован с опциями -fprofile-arcs -ftest-coverage.

If you are developing Linux or desktop applications with GNU tools, you  very likely are familiar with gcov: the GNU coverage tool. It collects data what parts of the code gets executed and represents that in different formats, great to check what is really used in the application code or what has been covered during multiple test runs.

GNU coverage is possible for resource constraint embedded systems too: it still needs some extra RAM and code space, but very well spent for gathering metrics and improves the firmware quality. As I wrote in “MCUXpresso IDE V11.3.0 for 2021” things are now easier to use, so here is a short tutorial how to use it.

Outline

For how gcov works, have a read at gcov for Embedded. This tutorial shows how to use gcov with the MCUXpresso IDE V11.3.0. As board I’m using the FRDM-K64F, and you can find the example project on GitHub.

To generate coverage we need:

• Eclipse with the gcov plugins (they are already installed in MCUXpresso IDE 11.3.0)
• GNU binaries without the ‘arm-none-eabi’ prefix: I use a batch file for this
• A project to collect coverage information

We will instrument source files go produce .gcno files on the host. The instrumented application will generate .gcda files we store on the host using semihosting. The gcov tool then will show the reports in the IDE or on the command line:

The files and project used in this article can be found on GitHub.

Creating Project

I recommend to get familiar with gcov using a small and bare metal project. I have created a project with the IDE and the MCUXpresso SDK.

Make sure the project is using newlib (nano) with semihosting:

This creates the project:

Linker Constructor Symbols

Each instrumented file will generate a special constructor which needs to be called later. To be able to call them, we need to include them into our binary and mark them with special symbols. This is done in MCUXpresso IDE with a special FreeMarker Linker script:

/************************************************
* start of main_text.ldt: *
************************************************/
. = ALIGN(4);
*(.text*)
/* added in template for gcov: */
. = ALIGN(4);
PROVIDE_HIDDEN (__init_array_start = .);
KEEP (*(SORT(.init_array.*)))
KEEP (*(.init_array*))
PROVIDE_HIDDEN (__init_array_end = .);
/************************************************ 
* end of main_text.ldt *
************************************************/

Create a file named main_text.ldt and place it into the folder linkscripts in the project root (or copy it from GitHub):

Support Files

To write the data, a few hooks and helpers are needed. You can find them in the ‘gcov’ folder of my project on GitHub:

Add it to the project; we will use it in the next step.

Init and Data Writing

The gcov library needs to be initialized. Include the header file:l

#include "../gcov/gcov_support.h"

Call

gcov_init(); /* initialize library */

at the start of main(). Then run the instrumented code. At the end, call

gcov_write();

to write the data;

Heap and Stack

The application on the board writes the collected data to the host via semi-hosting file I/O. Unfortunately file I/O is not very lightweight, and most issues with using gcov for embedded systems are because lack of stack and heap space.

Typically the default heap and stack size will not be enough, so I recommend to assign a good chunk of memory in case of issues: the more the better.

Instrumenting Source Files

Each file which shall be instrumented for coverage needs to have the following options added:

-fprofile-arcs -ftest-coverage

I recommend as a starter just to instrument one file, or very few.

Finally, add the option

-fprofile-arcs

to the linker settings to ensure it links with the proper library support.

💡 instead of -fprofile-arcs the option --coverage can be used.

Now it is a good time to perform a Project > Clean followed by a Project > Build. It shall now generate .gcno files in the output folder:

Collecting Coverage

Now you can run the application: it will collect information from the instrumented code and write the .gcda files on the host using semi-hosting file I/O:

Viewing Coverage Information

Double-click on any of the .gda files and it will open a graphical view:

Tadaaaaa! 🙂

Double-clicking on a line shows the information with colors in the source view:

Gcovr

If you want to use the gcov data outside of Eclipse, have a look at https://github.com/gcovr/gcovr. It has a feature to add and combine different coverage data files too.

Summary

Coverage tells which lines of code have been executed. This is very important to get good test coverage and can increase software quality. Traditionally coverage as GNU gcov has been used on host applications, but it is possible to use it for embedded targets as well. The latest NXP MCUXpresso IDE 11.3.0 makes it even easier as all the needed tools are already installed: that way I can start collecting coverage information from the target and view and analyze it on the host.

Happy covering 🙂

Links

• Adding GNU Coverage Tools to Eclipse
• MCUXpresso IDE V11.3.0 for 2021
• GNU Coverage Tool: https://gcc.gnu.org/onlinedocs/gcc/Gcov.html
• Code Coverage for Embedded Target with Eclipse, gcc and gcov: https://mcuoneclipse.com/2014/12/26/code-coverage-for-embedded-target-with-eclipse-gcc-and-gcov/
• Code Coverage with gcov, launchpad tools and Eclipse Kinetis Design Studio V3.0.0: https://mcuoneclipse.com/2015/05/31/code-coverage-with-gcov-launchpad-tools-and-eclipse-kinetis-design-studio-v3-0-0/
• Files of this project on GitHub: https://github.com/ErichStyger/mcuoneclipse/tree/master/Examples/MCUXpresso/FRDM-K64F/FRDM-K64F_gcov_bm