本文首发于 2016-03-30 15:34:34

引言

通常咱们评判一个 test case 好坏的规范之一是代码的覆盖率，一个好的 test case 应该笼罩到所有的代码。

那么问题来了，咱们怎么晓得这个 test case 有没有笼罩到所有的代码呢？

以 PostgreSQL 为例，咱们看看如何检测 C 语言程序的代码覆盖率。

C 代码覆盖率测试，须要用到 gcc 的配套工具gcov，还有一个可视化工具lcov。

1. 装置依赖

首先须要装置依赖 gcov 和 lcov 。

gcov 在 gcc 包中曾经蕴含了，lcov 是 ltp 的一个 gcov 扩大插件，用来产生HTML报告。

sudo apt install lcov

2. 编译、装置 PG

2.1. 编译选项介绍

首先介绍一下 PostgreSQL 的编译选项 --enable-coverage：

--enable-coverage       build with coverage testing instrumentation

这个编译项对应gcc的两个参数：-fprofile-arcs 和 -ftest-coverage。

# enable code coverage if --enable-coverageif test "$enable_coverage" = yes; then  if test "$GCC" = yes; then    CFLAGS="$CFLAGS -fprofile-arcs -ftest-coverage"  else    as_fn_error $? "--enable-coverage is supported only when using GCC" "$LINENO" 5  fifi

通过man gcc查看这两个参数的含意：

-fprofile-arcs           Add code so that program flow arcs are instrumented.  During execution the program records how many times each branch and call is executed and how many times it is taken or returns.  When           the compiled program exits it saves this data to a file called auxname.gcda for each source file.  The data may be used for profile-directed optimizations (-fbranch-probabilities), or for           test coverage analysis (-ftest-coverage).  Each object file's auxname is generated from the name of the output file, if explicitly specified and it is not the final executable, otherwise           it is the basename of the source file.  In both cases any suffix is removed (e.g. foo.gcda for input file dir/foo.c, or dir/foo.gcda for output file specified as -o dir/foo.o).--coverage           This option is used to compile and link code instrumented for coverage analysis.  The option is a synonym for -fprofile-arcs -ftest-coverage (when compiling) and -lgcov (when linking).           See the documentation for those options for more details.           *   Compile the source files with -fprofile-arcs plus optimization and code generation options.  For test coverage analysis, use the additional -ftest-coverage option.  You do not need to               profile every source file in a program.           *   Link your object files with -lgcov or -fprofile-arcs (the latter implies the former).           *   Run the program on a representative workload to generate the arc profile information.  This may be repeated any number of times.  You can run concurrent instances of your program, and               provided that the file system supports locking, the data files will be correctly updated.  Also "fork" calls are detected and correctly handled (double counting will not happen).           *   For profile-directed optimizations, compile the source files again with the same optimization and code generation options plus -fbranch-probabilities.           *   For test coverage analysis, use gcov to produce human readable information from the .gcno and .gcda files.  Refer to the gcov documentation for further information.           With -fprofile-arcs, for each function of your program GCC creates a program flow graph, then finds a spanning tree for the graph.  Only arcs that are not on the spanning tree have to be           instrumented: the compiler adds code to count the number of times that these arcs are executed.  When an arc is the only exit or only entrance to a block, the instrumentation code can be           added to the block; otherwise, a new basic block must be created to hold the instrumentation code.-ftest-coverage           Produce a notes file that the gcov code-coverage utility can use to show program coverage.  Each source file's note file is called auxname.gcno.  Refer to the -fprofile-arcs option above           for a description of auxname and instructions on how to generate test coverage data.  Coverage data matches the source files more closely if you do not optimize.

-fprofile-arcs：

-fprofile-arcs 用于产生 .c 文件对应的 .gcda 文件，.gcda 文件能够被用于 profile 驱动的优化，或者联合 gcov 来做代码笼罩剖析。

编译时尽量不要应用 -O 优化，这样代码笼罩数据 .gcda 能力尽可能和代码靠近。

当代码被调用时，.gcda 文件中对应的计数器会被批改，记录代码被调用的次数。

-ftest-coverage：

-ftest-coverage 这个选项用于产生 .c 文件的 .gcno 文件。这个文件生成后不会被批改。联合 .gcda，能够剖析测试代码覆盖率。

2.2. 编译装置

./configure --prefix=/opt/pgsql9.4.4 --with-pgport=1921 --with-perl --with-python --with-tcl --with-openssl --with-pam --with-ldap --with-libxml --with-libxslt --enable-thread-safety --enable-debug --enable-dtrace --enable-coveragegmake world && gmake install-world

装置好后，咱们会发现在源码目录中多了一些.gcda和.gcno的文件，每个.c文件都会对应这两个文件：

postgres@wslu-> lltotal 1.3M-rw-r--r-- 1 postgres postgres  22K Jun 10 03:29 gistbuildbuffers.c-rw------- 1 postgres postgres 1.6K Sep  7 14:42 gistbuildbuffers.gcda-rw-r--r-- 1 postgres postgres  15K Sep  7 14:38 gistbuildbuffers.gcno-rw-r--r-- 1 postgres postgres  70K Sep  7 14:38 gistbuildbuffers.o-rw-r--r-- 1 postgres postgres  37K Jun 10 03:29 gistbuild.c-rw------- 1 postgres postgres 2.2K Sep  7 14:42 gistbuild.gcda-rw-r--r-- 1 postgres postgres  20K Sep  7 14:38 gistbuild.gcno-rw-r--r-- 1 postgres postgres  92K Sep  7 14:38 gistbuild.o-rw-r--r-- 1 postgres postgres  43K Jun 10 03:29 gist.c-rw------- 1 postgres postgres 3.1K Sep  7 14:42 gist.gcda-rw-r--r-- 1 postgres postgres  29K Sep  7 14:38 gist.gcno-rw-r--r-- 1 postgres postgres  16K Jun 10 03:29 gistget.c-rw------- 1 postgres postgres 1.3K Sep  7 14:42 gistget.gcda-rw-r--r-- 1 postgres postgres  13K Sep  7 14:38 gistget.gcno-rw-r--r-- 1 postgres postgres  74K Sep  7 14:38 gistget.o-rw-r--r-- 1 postgres postgres 101K Sep  7 14:38 gist.o-rw-r--r-- 1 postgres postgres  39K Jun 10 03:29 gistproc.c-rw------- 1 postgres postgres 3.1K Sep  7 14:42 gistproc.gcda-rw-r--r-- 1 postgres postgres  31K Sep  7 14:38 gistproc.gcno-rw-r--r-- 1 postgres postgres  79K Sep  7 14:38 gistproc.o-rw-r--r-- 1 postgres postgres 9.1K Jun 10 03:29 gistscan.c-rw------- 1 postgres postgres  848 Sep  7 14:42 gistscan.gcda-rw-r--r-- 1 postgres postgres 6.7K Sep  7 14:38 gistscan.gcno-rw-r--r-- 1 postgres postgres  60K Sep  7 14:38 gistscan.o-rw-r--r-- 1 postgres postgres  24K Jun 10 03:29 gistsplit.c-rw------- 1 postgres postgres 1.5K Sep  7 14:42 gistsplit.gcda-rw-r--r-- 1 postgres postgres  15K Sep  7 14:38 gistsplit.gcno-rw-r--r-- 1 postgres postgres  68K Sep  7 14:38 gistsplit.o-rw-r--r-- 1 postgres postgres  21K Jun 10 03:29 gistutil.c-rw------- 1 postgres postgres 2.2K Sep  7 14:42 gistutil.gcda-rw-r--r-- 1 postgres postgres  20K Sep  7 14:38 gistutil.gcno-rw-r--r-- 1 postgres postgres  84K Sep  7 14:38 gistutil.o-rw-r--r-- 1 postgres postgres 7.1K Jun 10 03:29 gistvacuum.c-rw------- 1 postgres postgres  784 Sep  7 14:42 gistvacuum.gcda-rw-r--r-- 1 postgres postgres 7.3K Sep  7 14:38 gistvacuum.gcno-rw-r--r-- 1 postgres postgres  56K Sep  7 14:38 gistvacuum.o-rw-r--r-- 1 postgres postgres  14K Jun 10 03:29 gistxlog.c-rw------- 1 postgres postgres 1.2K Sep  7 14:42 gistxlog.gcda-rw-r--r-- 1 postgres postgres  12K Sep  7 14:38 gistxlog.gcno-rw-r--r-- 1 postgres postgres  50K Sep  7 14:38 gistxlog.o-rw-r--r-- 1 postgres postgres  538 Jun 10 03:29 Makefile-rw-r--r-- 1 postgres postgres  357 Sep  7 14:38 objfiles.txt-rw-r--r-- 1 postgres postgres  20K Jun 10 03:29 READMEpostgres@wslu-> pwd/opt/soft_bak/postgresql-9.4.4/src/backend/access/gist

注意事项：

源码文件目录的权限须要改为数据库启动用户的权限，否则无奈批改 .gcda 的值，也就无奈获取代码被调用的次数了。

root@wslu-> chown -R postgres:postgres /opt/soft_bak/postgresql-9.4.4

接下来咱们看看文件的变动，以 dbsize.c 中的两个获取 pg_database_size 的 C 函数为例：

postgres@wslu-> ls -la|grep dbsize-rw-r--r--  1 postgres postgres  19342 Jun 10 03:29 dbsize.c-rw-------  1 postgres postgres   2664 Sep  7 15:01 dbsize.gcda-rw-r--r--  1 postgres postgres  23272 Sep  7 14:38 dbsize.gcno-rw-r--r--  1 postgres postgres  89624 Sep  7 14:38 dbsize.o

调用一次：

postgres@wslu-> psqlpsql (9.4.4)Type "help" for help.postgres=# select pg_database_size(oid) from pg_database; pg_database_size ------------------          6898180          6889988         24742560          6898180          6898180          6898180(6 rows)postgres=# \q

再次查看：

postgres@wslu-> ls -la|grep dbsize-rw-r--r--  1 postgres postgres  19342 Jun 10 03:29 dbsize.c-rw-------  1 postgres postgres   2664 Sep  7 15:12 dbsize.gcda-rw-r--r--  1 postgres postgres  23272 Sep  7 14:38 dbsize.gcno-rw-r--r--  1 postgres postgres  89624 Sep  7 14:38 dbsize.o

dbsize.gcda 文件的批改工夫发送了变动，阐明方才咱们调用pg_database_size(oid) 时，调用了 dbsize.c 中的代码。对应的行计数器会发生变化。

3. 生成 HTML 报告

$ mkdir html$ cd html$ lcov --directory /opt/soft_bak/postgresql-9.4.4 --capture --output-file ./app.info# 如果你不须要所有的代码，批改以上目录即可，譬如只看 contrib 上面的代码覆盖率。$ genhtml ./app.info postgres@wslu-> lltotal 3.7Mdrwxrwxr-x 12 postgres postgres 4.0K Sep  7 15:02 access-rw-rw-r--  1 postgres postgres  141 Sep  7 15:02 amber.png-rw-rw-r--  1 postgres postgres 3.4M Sep  7 15:02 app.infodrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 bootstrapdrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 catalogdrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 commands-rw-rw-r--  1 postgres postgres  141 Sep  7 15:02 emerald.pngdrwxrwxr-x  2 postgres postgres  12K Sep  7 15:02 executordrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 foreign-rw-rw-r--  1 postgres postgres 9.7K Sep  7 15:02 gcov.css-rw-rw-r--  1 postgres postgres  167 Sep  7 15:02 glass.png-rw-rw-r--  1 postgres postgres  57K Sep  7 15:02 index.html-rw-rw-r--  1 postgres postgres  57K Sep  7 15:02 index-sort-f.html-rw-rw-r--  1 postgres postgres  57K Sep  7 15:02 index-sort-l.htmldrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 libdrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 libpqdrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 maindrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 nodesdrwxrwxr-x  3 postgres postgres 4.0K Sep  7 15:02 optdrwxrwxr-x  7 postgres postgres 4.0K Sep  7 15:02 optimizerdrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 parserdrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 portdrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 postmasterdrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 regexdrwxrwxr-x  3 postgres postgres 4.0K Sep  7 15:02 replicationdrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 rewrite-rw-rw-r--  1 postgres postgres  141 Sep  7 15:02 ruby.pngdrwxrwxr-x  3 postgres postgres 4.0K Sep  7 15:02 snowball-rw-rw-r--  1 postgres postgres  141 Sep  7 15:02 snow.pngdrwxrwxr-x 10 postgres postgres 4.0K Sep  7 15:02 storagedrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 tcopdrwxrwxr-x  2 postgres postgres 4.0K Sep  7 15:02 tsearch-rw-rw-r--  1 postgres postgres  117 Sep  7 15:02 updown.pngdrwxrwxr-x  3 postgres postgres 4.0K Sep  7 15:02 usrdrwxrwxr-x 14 postgres postgres 4.0K Sep  7 15:02 utils

4. 查看报告

浏览器中关上 index.html 即可查看。

后记

PostgreSQL 其实曾经在 Makefile 提供了生成代码笼罩 HTML 的 target 。

[root@wslu postgresql-9.4.4]# make coverage-html

产生的html目录如下：

[root@wslu postgresql-9.4.4]# cd coverage[root@wslu coverage]# lltotal 224-rw-r--r--  1 root root   141 Sep  7 19:17 amber.png-rw-r--r--  1 root root   141 Sep  7 19:17 emerald.png-rw-r--r--  1 root root  9893 Sep  7 19:17 gcov.css-rw-r--r--  1 root root   167 Sep  7 19:17 glass.png-rw-r--r--  1 root root 58737 Sep  7 19:18 index.html-rw-r--r--  1 root root 58730 Sep  7 19:18 index-sort-f.html-rw-r--r--  1 root root 58730 Sep  7 19:18 index-sort-l.html-rw-r--r--  1 root root   141 Sep  7 19:17 ruby.png-rw-r--r--  1 root root   141 Sep  7 19:17 snow.pngdrwxr-xr-x 11 root root  4096 Sep  7 19:18 src-rw-r--r--  1 root root   117 Sep  7 19:17 updown.pngdrwxr-xr-x  3 root root  4096 Sep  7 19:18 usr

每次对代码改变后，执行完 make check 或其余回归测试伎俩后，就能够执行 make coverage-html 了。

参考链接

1. Magus Test Archive
2. lcov
3. lcov readme
4. GitHub - linux-test-project/ltp: Linux Test Project http://linux-test-project.github.io/
5. Gcov (Using the GNU Compiler Collection (GCC))
6. CodeCoverage - PostgreSQL wiki
7. PostgreSQL: Documentation: devel: 33.5. Test Coverage Examination

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