Daily findings

This is a list of findings, or things I learn every day.

CMake enable_testing()

I never read it properly, now, something I learn:

1. enable_testing() add CTest into the build process.
2. CTest scans our CMakeLists.txt files and create a new CTestTestfile.cmake for
   each directory we specify add_test() in our CMakeLists.txt
3. When invoked from command line, CTest scan for these CTestTestfile.cmake to
   get list of tests to run
4. CTest is a test runner, who discovers tests, decide which tests to run and how
   to run test cases. Test could be either a unit test written by C++ test framework,
   or executable that needs additional argument and system environment. It also generates
   reports (? need to double check this use case)
5. Testing libraries like: Boost test, catch2, google tests are testing framework that
   includes functions, macros, etc, to help use write tests. They can be build into
   many executable files under our project.
6. Should call enable_testing() in top level CMake, so CTest can look at top level
   build directory and can traverse down to search for test cases, which make easier
   for us to run test each time

Facilitate looping

Don’t use infinite loop like while(true) {} , use something like:

    while (_iteration++ < MAX_ITERATION) {
        // loop body
    }

To avoid program stucks forever if we have some bugs. We can break early and debug the logic in development

One of my approach:

#define WHILE_TRUE(limit) for (int i = 0; (assert(i < limit), true); ++i) 

// now instead of writing

while (true) {
    // loop body
}

WHILE_TRUE(10000) {
    // loops 10k time max, assert when it goes too long
}

This only applies whenever I attempt to write a while(true) - an infinite loop, other loop that only iterates containers can skip this trick, if we try to do something clever to index by looping by index, it’s worth applying this trick too

CURL cookies

NOTE (hanasou): Maybe I understand this wrong

Use -c <path_to_cookies_file> option to make CURL store cookies and use it in later requests. I stuck in infinite chain of redirection between /login page because that site only use authorization tokens for first request and after that it uses cookies for accessing resources.

ibus cache

When add a new component xml file, try clear the cache first or the program won’t look into directory again. I have to clean ~/.cache/ibus/ in order to make it to work.

Debugging tips: Break or strace on system calls open, openat to find out why ibus doesn’t use my IBUS_COMPONENT_PATH. I used and saw it look into cache file only.

TODO: When debug the issue above, I observe that when I break on certain file in /user/ (I forgot the actual filename, I think it relates to us key mapping) , I cannot use the keyboard anymore: terminal freeze, firefox doesn’t get new key input. When I typed into terminal, every key stroke have a delay of ~15 second but time gap between strokes were exactly the same as how I typed: When I intenitonally typed slow, the time between those character was slow too. CPU usage was file, and system stat was normal. To reproduce: > Use gdb on ibus built with debug from repository. No other changes except > I disabled gtk2 and wayland. Break on open and openat at above. Then > continue multiple time and get the issue.