| *dev_tools.txt* Nvim |
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| NVIM REFERENCE MANUAL |
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| Tools and techniques for developing Nvim *dev-tools* |
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| The following advice is helpful when working on or debugging issues with Nvim |
| itself. |
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| TODO: merge |debug.txt| into here. |
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| Type |gO| to see the table of contents. |
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| ============================================================================== |
| Backtraces *dev-tools-backtrace* |
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| LINUX |
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| Core dumps are disabled by default on Ubuntu, CentOS and others. |
| To enable core dumps: |
| >bash |
| ulimit -c unlimited |
| < |
| On systemd-based systems getting a backtrace is as easy as: |
| >bash |
| coredumpctl -1 gdb |
| < |
| `coredumpctl` is an optional tool, so you may need to install it: |
| >bash |
| sudo apt install systemd-coredump |
| < |
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| The full backtrace is most useful; please send us the `backtrace.txt` file |
| when reporting a bug related to a crash: |
| >bash |
| 2>&1 coredumpctl -1 gdb | tee -a backtrace.txt |
| (gdb) thread apply all bt full |
| < |
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| On systems without `coredumpctl`, you may find a `core` dump file appearing |
| in the current directory or in other locations. On Linux systems where |
| `apport` is installed (such as Ubuntu), the directory where core dump files |
| are saved can be `/var/lib/apport/coredump` or elsewhere, depending on the |
| system configuration (see `/proc/sys/kernel/core_pattern`). See also: |
| https://stackoverflow.com/a/18368068 |
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| To get a backtrace from the `./core` dump file: |
| >bash |
| gdb build/bin/nvim ./core 2>&1 | tee backtrace.txt |
| (gdb) thread apply all bt full |
| < |
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| MACOS |
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| If `nvim` crashes, you can see the backtrace in `Console.app` (under "Crash |
| Reports" or "User Diagnostic Reports" for older macOS versions). |
| >bash |
| open -a Console |
| < |
| You may also want to enable core dumps on macOS. To do this, first make sure |
| the `/cores/` directory exists and is writable: |
| >bash |
| sudo mkdir /cores |
| sudo chown root:admin /cores |
| sudo chmod 1775 /cores |
| < |
| Then set the core size limit to `unlimited`: |
| >bash |
| ulimit -c unlimited |
| < |
| Note that this is done per shell process. If you want to make this the default |
| for all shells, add the above line to your shell's init file (e.g. `~/.bashrc` |
| or similar). |
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| You can then open the core file in `lldb`: |
| >bash |
| lldb -c /cores/core.12345 |
| < |
| Apple's documentation archive has some other useful information |
| https://developer.apple.com/library/archive/technotes/tn2124/_index.html#//apple_ref/doc/uid/DTS10003391-CH1-SECCOREDUMPS, |
| but note that some of the things on this page are out of date (such as enabling |
| core dumps with `/etc/launchd.conf`). |
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| ============================================================================== |
| Gdb *dev-tools-gdb* |
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| USING GDB TO STEP THROUGH FUNCTIONAL TESTS |
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| Use `TEST_TAG` to run tests matching busted tags (of the form `#foo` e.g. |
| `it("test #foo ...", ...)`): |
| >bash |
| GDB=1 TEST_TAG=foo make functionaltest |
| < |
| Then, in another terminal: |
| >bash |
| gdb build/bin/nvim |
| (gdb) target remote localhost:7777 |
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| -- See `nvim_argv` in https://github.com/neovim/neovim/blob/master/test/functional/testnvim.lua. |
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| USING LLDB TO STEP THROUGH UNIT TESTS |
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| > |
| lldb .deps/usr/bin/luajit -- .deps/usr/bin/busted --lpath="./build/?.lua" test/unit/ |
| < |
| USING GDB |
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| To attach to a running `nvim` process with a pid of 1234 (Tip: the pid of a |
| running Nvim instance can be obtained by calling |getpid()|), for instance: |
| >bash |
| gdb -tui -p 1234 build/bin/nvim |
| < |
| The `gdb` interactive prompt will appear. At any time you can: |
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| - `break foo` to set a breakpoint on the `foo()` function |
| - `n` to step over the next statement |
| - `<Enter>` to repeat the last command |
| - `s` to step into the next statement |
| - `c` to continue |
| - `finish` to step out of the current function |
| - `p zub` to print the value of `zub` |
| - `bt` to see a backtrace (callstack) from the current location |
| - `CTRL-x CTRL-a` or `tui enable` to show a TUI view of the source file in the |
| current debugging context. This can be extremely useful as it avoids the |
| need for a gdb "frontend". |
| - `<up>` and `<down>` to scroll the source file view |
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| GDB REVERSE DEBUGGING |
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| - `set record full insn-number-max unlimited` |
| - `continue` for a bit (at least until `main()` is executed |
| - `record` |
| - provoke the bug, then use `revert-next`, `reverse-step`, etc. to rewind the |
| debugger |
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| USING GDBSERVER |
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| You may want to connect multiple `gdb` clients to the same running `nvim` |
| process, or you may want to connect to a remote `nvim` process with a local |
| `gdb`. Using `gdbserver`, you can attach to a single process and control it |
| from multiple `gdb` clients. |
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| Open a terminal and start `gdbserver` attached to `nvim` like this: |
| >bash |
| gdbserver :6666 build/bin/nvim 2> gdbserver.log |
| < |
| `gdbserver` is now listening on port 6666. You then need to attach to this |
| debugging session in another terminal: |
| >bash |
| gdb build/bin/nvim |
| < |
| Once you've entered `gdb`, you need to attach to the remote session: |
| > |
| (gdb) target remote localhost:6666 |
| < |
| In case gdbserver puts the TUI as a background process, the TUI can become |
| unable to read input from pty (and receives SIGTTIN signal) and/or output data |
| (SIGTTOU signal). To force the TUI as the foreground process, you can add |
| >c |
| signal (SIGTTOU, SIG_IGN); |
| if (!tcsetpgrp(data->input.in_fd, getpid())) { |
| perror("tcsetpgrp failed"); |
| } |
| < |
| to `tui.c:terminfo_start`. |
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| USING GDBSERVER IN TMUX |
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| Consider using a custom makefile |
| https://github.com/neovim/neovim/blob/master/BUILD.md#custom-makefile to |
| quickly start debugging sessions using the `gdbserver` method mentioned above. |
| This example `local.mk` will create the debugging session when you type `make |
| debug`. |
| >make |
| .PHONY: dbg-start dbg-attach debug build |
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| build: |
| @$(MAKE) nvim |
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| dbg-start: build |
| @tmux new-window -n 'dbg-neovim' 'gdbserver :6666 ./build/bin/nvim -D' |
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| dbg-attach: |
| @tmux new-window -n 'dbg-cgdb' 'cgdb -x gdb_start.sh ./build/bin/nvim' |
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| debug: dbg-start dbg-attach |
| < |
| Here `gdb_start.sh` includes `gdb` commands to be called when the debugger |
| starts. It needs to attach to the server started by the `dbg-start` rule. For |
| example: |
| > |
| (gdb) target remote localhost:6666 |
| (gdb) br main |
| < |
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| vim:tw=78:ts=8:et:ft=help:norl: |
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