Difference between revisions of "Testing removal of ifdef or configure checks"
(include hint from Thomas Nagy on getting CPP output for just one file) |
(remove space correctly refer to gcc-E script name (not an direct gcc -E invocation)) |
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Line 13: | Line 13: | ||
git checkout origin/master | git checkout origin/master | ||
git clean -x -f -d | git clean -x -f -d | ||
− | CC="gcc -E" ./configure.developer && make -j | + | CC="gcc-E" ./configure.developer && make -j |
mv bin /tmp/master-bin | mv bin /tmp/master-bin | ||
git checkout newbranch | git checkout newbranch | ||
git clean -x -f -d | git clean -x -f -d | ||
− | CC="gcc -E" ./configure.developer && make -j | + | CC="gcc-E" ./configure.developer && make -j |
===Reading the results=== | ===Reading the results=== |
Latest revision as of 21:58, 14 March 2020
Contents
#ifdef removal is risky
Large-scale removal of "unused" ifdef or the configure checks that produce #defines is an important, but risky task.
It is difficult (and time consuming) to prove that the code is unused and that there is no change to the compiled output.
A script to help obtain CPP output
File:Gcc-E.py.txt is a Python script that wraps gcc -E (to get the CPP output) to attempt to solve this dilemma, so as to provide a result that can be reasoned with via tools like dirdiff
Getting the results
git checkout origin/master git clean -x -f -d CC="gcc-E" ./configure.developer && make -j mv bin /tmp/master-bin git checkout newbranch git clean -x -f -d CC="gcc-E" ./configure.developer && make -j
Reading the results
dirdiff /tmp/master-bin bin
or
diff -ur --ignore-matching-lines="^#" /tmp/master-bin/ bin> /tmp/diff
Getting just one file's CPP output
Thanks to waf author Thomas Nagy
WAF_CMD_FORMAT=string PYTHONHASHSEED=1 WAF_MAKE=1 ./buildtools/bin/waf -v build
Then just edit the command to add the -E (and perhaps a new output file).