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laforge, 12/31/2020 01:00 PM
add note about useful asan option

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h1. Development tools
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h2. C tools
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* @Lindent@ (from kernel source), reformat C code to the Linux kernel (and osmocom) coding standards
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* @cflow@ to generate flow-graphs from source code
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h2. Patches
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* @git format-patch -1@, generate a patch
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* @checkpatch.pl@, check patches for common errors (Ignore x-signed-off-by)
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* @make distcheck@ catches quite a few errors, run it before sending patches.
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* @git send-email -1@ Send a patch to the mailing list (after configuration)
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h2. Testing
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* @make check@: run it and don't introduce regressions
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* @make distcheck@: run it to make sure that @make dist@ contains everything needed and you didn't forget to add any files to Makefile.am
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* Our extensive [[Titan_TTCN3_Testsuites]]
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h2. AddressSanitizer
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All Osmocom CNI projects support building iwth @./configure --enable-sanitize@, which enables support for "AddressSanitizer":https://github.com/google/sanitizers/wiki/AddressSanitizer
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This is extremely useful in finding a variety of problems, such as use-after-free.
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h3. meaniungful backtraces
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Often  the backtraces you get from asan are too short to figure out where an allocation/free has happened, like:
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<pre>
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0x612000000eb8 is located 248 bytes inside of 296-byte region [0x612000000dc0,0x612000000ee8)
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freed by thread T0 here:
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    #0 0x7f42477d9b6f in __interceptor_free ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:123
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    #1 0x7f4246b2678a in _tc_free_internal ../../talloc.c:1221
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previously allocated by thread T0 here:
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    #0 0x7f42477d9e8f in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145
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    #1 0x7f4246b28ecb in __talloc_with_prefix ../../talloc.c:782
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</pre>
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In this case, it is recommended to run with the environment variable @ASAN_OPTIONS="fast_unwind_on_malloc=0"@, which will produce a much more meaningful backtrace. The same bug as the above example now looks like this:
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<pre>
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0x612000000eb8 is located 248 bytes inside of 296-byte region [0x612000000dc0,0x612000000ee8)
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freed by thread T0 here:
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    #0 0x7f5c3e64bb6f in __interceptor_free ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:123
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    #1 0x7f5c3d99878a in _tc_free_internal ../../talloc.c:1221
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    #2 0x7f5c3daa648e in fsm_free_or_steal /space/home/laforge/projects/git/libosmocore/src/fsm.c:116
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    #3 0x7f5c3daa648e in osmo_fsm_inst_free /space/home/laforge/projects/git/libosmocore/src/fsm.c:574
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    #4 0x7f5c3daab8ef in _osmo_fsm_inst_term /space/home/laforge/projects/git/libosmocore/src/fsm.c:959
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    #5 0x7f5c3daadb09 in fsm_tmr_cb /space/home/laforge/projects/git/libosmocore/src/fsm.c:337
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    #6 0x7f5c3da893a6 in osmo_timers_update /space/home/laforge/projects/git/libosmocore/src/timer.c:273
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    #7 0x7f5c3da8cf62 in _osmo_select_main /space/home/laforge/projects/git/libosmocore/src/select.c:373
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    #8 0x7f5c3da8d548 in osmo_select_main /space/home/laforge/projects/git/libosmocore/src/select.c:417
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    #9 0x55b16ce4705c in main /space/home/laforge/projects/git/osmo-cbc/src/cbc_main.c:216
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    #10 0x7f5c3cd63d09 in __libc_start_main ../csu/libc-start.c:308
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    #11 0x55b16ce47649 in _start (/space/home/laforge/projects/git/osmo-cbc/src/osmo-cbc+0x2a649)
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previously allocated by thread T0 here:
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    #0 0x7f5c3e64be8f in __interceptor_malloc ../../../../src/libsanitizer/asan/asan_malloc_linux.cpp:145
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    #1 0x7f5c3d99aecb in __talloc_with_prefix ../../talloc.c:782
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    #2 0x7f5c3d99b8a6 in __talloc ../../talloc.c:824
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    #3 0x7f5c3d99b8a6 in _talloc_named_const ../../talloc.c:981
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    #4 0x7f5c3d99b8a6 in _talloc_zero ../../talloc.c:2422
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    #5 0x7f5c3daa4fcd in osmo_fsm_inst_alloc /space/home/laforge/projects/git/libosmocore/src/fsm.c:445
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    #6 0x55b16ce4c3c8 in cbsp_cbc_accept_cb /space/home/laforge/projects/git/osmo-cbc/src/cbsp_server.c:127
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    #7 0x7f5c3d931288 in osmo_stream_srv_fd_cb /space/home/laforge/projects/git/libosmo-netif/src/stream.c:880
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    #8 0x7f5c3da8d1b1 in poll_disp_fds /space/home/laforge/projects/git/libosmocore/src/select.c:350
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    #9 0x7f5c3da8d1b1 in _osmo_select_main /space/home/laforge/projects/git/libosmocore/src/select.c:378
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    #10 0x7f5c3da8d548 in osmo_select_main /space/home/laforge/projects/git/libosmocore/src/select.c:417
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    #11 0x55b16ce4705c in main /space/home/laforge/projects/git/osmo-cbc/src/cbc_main.c:216
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    #12 0x7f5c3cd63d09 in __libc_start_main ../csu/libc-start.c:308
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    #13 0x55b16ce47649 in _start (/space/home/laforge/projects/git/osmo-cbc/src/osmo-cbc+0x2a649)
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</pre>
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h2. Misc
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* pahole (dwarves), http://www.ohloh.net/p/pahole See the memory layout of structures
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* gdb, debugging
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* valgrind, http://valgrind.org/, dynamic analysis of memory management/threading
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* mudflap (gcc option), check array/pointer accesses. See http://zecke.blogspot.com/2012/10/know-your-tools-mudflap.html
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h2. Python tools
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h3. Formatting
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* pep8, https://pypi.python.org/pypi/pep8 Check formatting for pep8 compliance
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* autopep8, https://github.com/hhatto/autopep8 Reformat code to be pep8-complient
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h3. Checking/analysis
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* pyflakes, https://pypi.python.org/pypi/pyflakes Statically find some errors
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