CDT-LSP editor window crashes with a simple "Error" in the Editor window, whenever clangd gets restarted because compile_commands.json changes

[astrangeguy]

Nothing happening in workspace/.metadata/.log
Nothing in the Error Log view

Clangd shuts down and restarts cleanly whenever I run a build that overwrites compile_commands.json, but all editor windows look like the one in the screenshot

[ghentschke]

Hm, strange behavior. Can you tell something more about your IDE (vanilla Eclipse CDT or some vendor specific, Eclipse and CDT version as well as your OS.

Error is the only displayed text?

[ghentschke]

Which clangd are you using?
And a screenshot of your clangd settings would be helpful: Preferences --> C/C++ --> Editor (LSP) --> clangd.
Please enable the Log to Console option and set --log=info in the Additional options box.

[astrangeguy]

This is the clangd option pane:

And here's the log output during the crash.

I've switched to a non-C file, did a rebuild, switched back and it crashed

I[07:43:38.611] clangd version 20.1.2 (https://github.com/llvm/llvm-project 58df0ef89dd64126512e4ee27b4ac3fd8ddf6247)
I[07:43:38.611] Features: linux
I[07:43:38.611] PID: 170190
I[07:43:38.611] Working directory: /home/ak89
I[07:43:38.611] argv[0]: /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/bin/clangd
I[07:43:38.611] argv[1]: --clang-tidy
I[07:43:38.611] argv[2]: --background-index
I[07:43:38.611] argv[3]: --completion-style=detailed
I[07:43:38.611] argv[4]: --query-driver=/opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/bin/arm-ostl-linux-gnueabi/*
I[07:43:38.611] argv[5]: --function-arg-placeholders=1
I[07:43:38.611] argv[6]: --log=info
I[07:43:38.611] Starting LSP over stdin/stdout
I[07:43:38.612] <-- initialize("1")
I[07:43:38.613] --> reply:initialize("1") 1 ms
I[07:43:38.618] <-- initialized
I[07:43:38.619] <-- textDocument/didOpen
I[07:43:38.620] --> textDocument/publishDiagnostics
I[07:43:38.620] <-- textDocument/inlayHint("2")
I[07:43:38.620] Loaded compilation database from /home/ak89/workspace/a7-example-project/./compile_commands.json
I[07:43:38.621] --> window/workDoneProgress/create(0)
I[07:43:38.621] Enqueueing 2 commands for indexing
I[07:43:38.624] <-- reply(0)
I[07:43:38.624] --> $/progress
I[07:43:38.624] --> $/progress
I[07:43:38.639] System includes extractor: successfully executed /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/x86_64-ostl_sdk-linux/usr/bin/arm-ostl-linux-gnueabi/arm-ostl-linux-gnueabi-gcc
	got includes: "/opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi/usr/lib/arm-ostl-linux-gnueabi/12.2.0/include, /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/lib/arm-ostl-linux-gnueabi/gcc/arm-ostl-linux-gnueabi/12.2.0/include-fixed, /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi/usr/include/"
	got target: "arm-ostl-linux-gnueabi"
I[07:43:38.640] ASTWorker building file /home/ak89/workspace/a7-example-project/src/main.c version 1 with command 
[/home/ak89/workspace/a7-example-project/Debug]
/opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/bin/arm-ostl-linux-gnueabi/arm-ostl-linux-gnueabi-gcc --sysroot=/opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi -DDEBUG=1 -mthumb -mfpu=neon-vfpv4 -mfloat-abi=hard -mcpu=cortex-a7 -g -flto -fno-fat-lto-objects -Wall -Wextra -pedantic -std=gnu2x -o CMakeFiles/a7-example-project.dir/src/main.c.o -c -isystem /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi/usr/lib/arm-ostl-linux-gnueabi/12.2.0/include -isystem /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/lib/arm-ostl-linux-gnueabi/gcc/arm-ostl-linux-gnueabi/12.2.0/include-fixed -isystem /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi/usr/include/ --target=arm-ostl-linux-gnueabi -resource-dir=/opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/lib/clang/20 -- /home/ak89/workspace/a7-example-project/src/main.c
I[07:43:38.643] --> $/progress
I[07:43:38.643] --> $/progress
I[07:43:38.656] <-- textDocument/documentSymbol("3")
I[07:43:38.707] Built preamble of size 694592 for file /home/ak89/workspace/a7-example-project/src/main.c version 1 in 0.06 seconds
I[07:43:38.707] Indexing c23 standard library in the context of /home/ak89/workspace/a7-example-project/src/main.c
I[07:43:38.726] --> textDocument/publishDiagnostics
I[07:43:38.726] --> reply:textDocument/inlayHint("2") 105 ms
I[07:43:38.726] --> reply:textDocument/documentSymbol("3") 70 ms
I[07:43:38.892] Indexed c23 standard library: 2961 symbols, 17 filtered
I[07:43:38.951] <-- textDocument/documentLink("4")
I[07:43:38.952] <-- textDocument/semanticTokens/full("5")
I[07:43:38.952] --> reply:textDocument/documentLink("4") 1 ms
I[07:43:38.953] --> reply:textDocument/semanticTokens/full("5") 1 ms
I[07:43:38.957] <-- textDocument/foldingRange("6")
I[07:43:38.958] --> reply:textDocument/foldingRange("6") 0 ms
I[07:43:39.070] <-- textDocument/documentHighlight("7")
I[07:43:39.070] --> reply:textDocument/documentHighlight("7") 0 ms
I[07:43:39.156] <-- textDocument/documentSymbol("8")
I[07:43:39.156] --> reply:textDocument/documentSymbol("8") 0 ms
I[07:43:47.981] <-- shutdown("9")                                                         //!!! Rebuild project before this
I[07:43:47.981] --> reply:shutdown("9") 0 ms
I[07:43:48.093] clangd version 20.1.2 (https://github.com/llvm/llvm-project 58df0ef89dd64126512e4ee27b4ac3fd8ddf6247)
I[07:43:48.093] Features: linux
I[07:43:48.093] PID: 170342
I[07:43:48.093] Working directory: /home/ak89
I[07:43:48.093] argv[0]: /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/bin/clangd
I[07:43:48.093] argv[1]: --clang-tidy
I[07:43:48.093] argv[2]: --background-index
I[07:43:48.093] argv[3]: --completion-style=detailed
I[07:43:48.093] argv[4]: --query-driver=/opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/bin/arm-ostl-linux-gnueabi/*
I[07:43:48.093] argv[5]: --function-arg-placeholders=1
I[07:43:48.093] argv[6]: --log=info
I[07:43:48.093] Starting LSP over stdin/stdout
I[07:43:48.093] <-- initialize("1")
I[07:43:48.095] --> reply:initialize("1") 1 ms
I[07:43:48.099] <-- initialized
I[07:43:49.781] <-- textDocument/didOpen    //!!! The crash occurred after this
I[07:43:49.782] --> textDocument/publishDiagnostics
I[07:43:49.782] Loaded compilation database from /home/ak89/workspace/a7-example-project/./compile_commands.json
I[07:43:49.783] --> window/workDoneProgress/create(0)
I[07:43:49.783] Enqueueing 2 commands for indexing
I[07:43:49.784] <-- reply(0)
I[07:43:49.784] --> $/progress
I[07:43:49.784] --> $/progress
I[07:43:49.797] --> $/progress
I[07:43:49.797] --> $/progress
I[07:43:49.799] System includes extractor: successfully executed /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/x86_64-ostl_sdk-linux/usr/bin/arm-ostl-linux-gnueabi/arm-ostl-linux-gnueabi-gcc
	got includes: "/opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi/usr/lib/arm-ostl-linux-gnueabi/12.2.0/include, /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/lib/arm-ostl-linux-gnueabi/gcc/arm-ostl-linux-gnueabi/12.2.0/include-fixed, /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi/usr/include/"
	got target: "arm-ostl-linux-gnueabi"
I[07:43:49.799] ASTWorker building file /home/ak89/workspace/a7-example-project/src/main.c version 1 with command 
[/home/ak89/workspace/a7-example-project/Debug]
/opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/bin/arm-ostl-linux-gnueabi/arm-ostl-linux-gnueabi-gcc --sysroot=/opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi -DDEBUG=1 -mthumb -mfpu=neon-vfpv4 -mfloat-abi=hard -mcpu=cortex-a7 -g -flto -fno-fat-lto-objects -Wall -Wextra -pedantic -std=gnu2x -o CMakeFiles/a7-example-project.dir/src/main.c.o -c -isystem /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi/usr/lib/arm-ostl-linux-gnueabi/12.2.0/include -isystem /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/lib/arm-ostl-linux-gnueabi/gcc/arm-ostl-linux-gnueabi/12.2.0/include-fixed -isystem /opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/share/cmake/../../../../../sysroots/cortexa7t2hf-neon-vfpv4-ostl-linux-gnueabi/usr/include/ --target=arm-ostl-linux-gnueabi -resource-dir=/opt/st/osd32mp1-red/4.0.11-snapshot/sysroots/x86_64-ostl_sdk-linux/usr/lib/clang/20 -- /home/ak89/workspace/a7-example-project/src/main.c
I[07:43:49.848] Built preamble of size 694592 for file /home/ak89/workspace/a7-example-project/src/main.c version 1 in 0.05 seconds
I[07:43:49.848] Indexing c23 standard library in the context of /home/ak89/workspace/a7-example-project/src/main.c
I[07:43:49.863] --> textDocument/publishDiagnostics
I[07:43:50.018] Indexed c23 standard library: 2961 symbols, 17 filtered

[astrangeguy]

Eclipse itself shows nothing. Nothing in the Error Log view. and nothing in the console (-consolelog -debug) during the crash.

Anything else I could do to get more logging?

[ghentschke]

Thanks for the info. If to setup a Linux machine and try to reproduce this error. Which Linux distribution are u using?

Does this happen with every C file or C project? E.g. also with a simple Hello World template project?

[astrangeguy]

This is a Kubuntu 25.04, and yes, it crashes even with the most simple new project:

CMakeLists.txt

project(
  cdt-lsp-test
  LANGUAGES C CXX
)

set(SOURCES "hello.c")

add_executable(${PROJECT_NAME}
  ${SOURCES}
)

hello.c

#include <stdio.h>
int main()
{
    puts("Hello World!");
}

hello.h

#define HELLO "this is just to test if it crashes on a totally unrelated non-included file. It does"

[astrangeguy]

I also tested it with the clangd provided by ubuntu (clangd-20) instead of my custom built one from a yocto toolchain. Same crash.

[ghentschke]

Okay, now I need your Eclipse IDE version and CDT and CDT-LSP version from Help -->About Eclipse IDE --> Installation Detail

[astrangeguy]

It should be the most recent ones

[astrangeguy]

Ok, I was wrong about the Ubuntu version. It's 24.04 LTS 3

And I managed to get the same error with a fresh install of Eclipse and just the bare bones of plugins
CDT
CDT-LSP
cmake4eclipse

the issue stems from the the cmake4eclipse plugin which deletes CMakeCache.txt files whenever a CMakeLists.txt gets modified or their "Force re-creation with each build" is enabled.

When I disable that option and don't edit any CMakeLists.txt's then the crash of the editor and restart of clangd doesn't happen on rebuild. But that's just because compile_commands.json doesn't get regenerated.

[astrangeguy]

Ok. I can recreate the issue just by "touch compile_commands.json" which forces clangd to restart and crash the editor.