CDT fails to generate correct commands in compile_commands.json file

[dc42]

Using Eclipse CDT 4.35.0 (build ID 20250306-0812) under Windows, cross compiling for ARM gcc. When the LSP editor is selected and logging is enabled, the output in the console window is as follows:

I[14:59:50.488] clangd version 18.1.8
I[14:59:50.488] Features: windows
I[14:59:50.488] PID: 36888
I[14:59:50.488] Working directory: C:\Users\David\eclipse\cpp-2024-06\eclipse
I[14:59:50.488] argv[0]: C:\Program Files\LLVM\bin\clangd.exe
I[14:59:50.488] argv[1]: --clang-tidy
I[14:59:50.488] argv[2]: --background-index
I[14:59:50.488] argv[3]: --completion-style=detailed
I[14:59:50.488] argv[4]: --pretty
I[14:59:50.488] argv[5]: --query-driver=C:\Program Files (x86)\Arm GNU Toolchain arm-none-eabi\13.2 Rel1\bin\*g++.exe,C:\Program Files (x86)\Arm GNU Toolchain arm-none-eabi\13.2 Rel1\bin\*gcc.exe
I[14:59:50.488] argv[6]: --function-arg-placeholders=1
I[14:59:50.493] Starting LSP over stdin/stdout
I[14:59:50.938] <-- initialize("1")
I[14:59:50.941] --> reply:initialize("1") 2 ms
I[14:59:51.018] <-- initialized
I[14:59:51.033] <-- textDocument/didOpen
I[14:59:51.036] --> textDocument/publishDiagnostics
I[14:59:51.036] <-- textDocument/documentLink("2")
I[14:59:51.036] Loaded compilation database from C:\Eclipse\Firmware-3.6\RRFLibraries\SAME70_RTOS\compile_commands.json
I[14:59:51.036] <-- textDocument/semanticTokens/full("3")
I[14:59:51.038] --> window/workDoneProgress/create(0)
I[14:59:51.038] Enqueueing 43 commands for indexing
I[14:59:51.042] <-- textDocument/inlayHint("4")
E[14:59:51.042] System include extraction: driver arm-none-eabi- not found in PATH
I[14:59:51.046] ASTWorker building file C:\Eclipse\Firmware-3.6\RRFLibraries\src\General\SimpleMath.cpp version 1 with command 
[C:/Eclipse/Firmware-3.6/RRFLibraries]
"C:\\Program Files\\LLVM\\bin\\arm-none-eabi-" -std=gnu++17 -D__SAME70Q21__ -DRTOS "-IC:\\Eclipse\\Firmware-3.6\\FreeRTOS\\src\\include" "-IC:\\Eclipse\\Firmware-3.6\\FreeRTOS\\src\\portable\\GCC\\ARM_CM7\\r0p1" -O2 -Wall -c -mcpu=cortex-m7 -mthumb -fno-math-errno -mfpu=fpv5-d16 -mfloat-abi=hard -mfp16-format=ieee -mno-unaligned-access -ffunction-sections -fdata-sections -fno-threadsafe-statics -fno-rtti -fno-exceptions -nostdlib -Wundef -Wdouble-promotion -fsingle-precision-constant -Wa,-ahl=$*.s -o C:/Eclipse/Firmware-3.6/RRFLibraries/SAME70_RTOS/src/General/SimpleMath.o "-resource-dir=C:\\Program Files\\LLVM\\lib\\clang\\18" -- "C:\\Eclipse\\Firmware-3.6\\RRFLibraries\\src\\General\\SimpleMath.cpp"
I[14:59:51.060] <-- reply(0)
I[14:59:51.060] --> $/progress
I[14:59:51.060] --> $/progress
I[14:59:51.094] --> textDocument/publishDiagnostics
I[14:59:51.095] Loaded compilation database from C:\Eclipse\Firmware-3.6\FreeRTOS\SAME51\compile_commands.json
I[14:59:51.161] --> $/progress
I[14:59:51.161] --> $/progress
I[14:59:51.161] --> $/progress
I[14:59:51.161] --> $/progress
I[14:59:51.161] --> $/progress
I[14:59:51.161] --> $/progress
I[14:59:51.161] --> $/progress
I[14:59:51.161] --> $/progress
I[14:59:51.161] --> $/progress
I[14:59:51.161] --> $/progress
I[14:59:51.161] --> $/progress
I[14:59:51.162] --> $/progress
I[14:59:51.162] --> $/progress
I[14:59:51.162] --> $/progress
I[14:59:51.162] --> $/progress
I[14:59:51.162] --> $/progress
I[14:59:51.162] --> $/progress
I[14:59:51.162] --> $/progress
E[14:59:51.172] System include extraction: driver m-none-eabi- not found in PATH
E[14:59:51.172] System include extraction: driver m-none-eabi- not found in PATH
E[14:59:51.172] System include extraction: driver m-none-eabi- not found in PATH
E[14:59:51.172] System include extraction: driver m-none-eabi- not found in PATH
E[14:59:51.172] System include extraction: driver m-none-eabi- not found in PATH
E[14:59:51.172] System include extraction: driver m-none-eabi- not found in PATH
...

The errors appear to be because the compile_commands.json file does not contain the G++ or GCC command, just the prefix. Here is the start of compile_commands.json:

[
  {
    "directory": "C:/Eclipse/Firmware-3.6/RepRapFirmware",
    "command": "arm-none-eabi- -std\u003dgnu++17 -D__SAME70Q20B__ -DRTOS -DDUET3_MB6HC -DMQTTC_PAL_FILE\u003d\"Networking/MQTT/mqtt_pal.h\" -D_XOPEN_SOURCE -I\"C:\\Eclipse\\Firmware-3.6\\LibTinyusb\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\" -I\"C:\\Eclipse\\Firmware-3.6\\FreeRTOS\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\\SAM4S_4E_E70\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\\SAM4S_4E_E70\\asf\\common\\utils\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\\SAM4S_4E_E70\\asf\\sam\\utils\\cmsis\\same70\\include\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\\arm\\CMSIS\\5.4.0\\CMSIS\\Core\\Include\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\\SAM4S_4E_E70\\SAME70\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\\SAM4S_4E_E70\\asf\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\\SAM4S_4E_E70\\asf\\sam\\utils\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\\SAM4S_4E_E70\\asf\\sam\\utils\\preprocessor\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\\SAM4S_4E_E70\\asf\\sam\\utils\\header_files\" -I\"C:\\Eclipse\\Firmware-3.6\\CoreN2G\\src\\SAM4S_4E_E70\\asf\\sam\\drivers\" -I\"C:\\Eclipse\\Firmware-3.6\\RepRapFirmware\\src\" -I\"C:\\Eclipse\\Firmware-3.6\\RepRapFirmware\\src\\Hardware\\SAME70\" -I\"C:\\Eclipse\\Firmware-3.6\\RepRapFirmware\\src\\Networking\" -I\"C:\\Eclipse\\Firmware-3.6\\RepRapFirmware\\src\\Networking\\LwipEthernet\\Lwip\" -I\"C:\\Eclipse\\Firmware-3.6\\RepRapFirmware\\src\\Networking\\LwipEthernet\\Lwip\\src\\include\" -I\"C:\\Eclipse\\Firmware-3.6\\RepRapFirmware\\src\\Networking\\MQTT\\MQTT_C\\include\" -I\"C:\\Eclipse\\Firmware-3.6\\WiFiSocketServerRTOS\\src\\include\" -I\"C:\\Eclipse\\Firmware-3.6\\FreeRTOS\\src\\include\" -I\"C:\\Eclipse\\Firmware-3.6\\FreeRTOS\\src\\portable\\GCC\\ARM_CM7\\r0p1\" -I\"C:\\Eclipse\\Firmware-3.6\\RRFLibraries\\src\" -I\"C:\\Eclipse\\Firmware-3.6\\CANlib\\src\" -O2 -Wall -c -mcpu\u003dcortex-m7 -mthumb -fno-math-errno -mfpu\u003dfpv5-d16 -mfloat-abi\u003dhard -mfp16-format\u003dieee -mno-unaligned-access -ffunction-sections -fdata-sections -fno-threadsafe-statics -fno-rtti -fexceptions -nostdlib -Wundef -Wdouble-promotion -Werror\u003dreturn-type -Wsuggest-override -fsingle-precision-constant \"-Wa,-ahl\u003d$*.s\" -fstack-usage -o \"C:/Eclipse/Firmware-3.6/RepRapFirmware/Duet3_MB6HC/src/Accelerometers/Accelerometers.o\" \"C:/Eclipse/Firmware-3.6/RepRapFirmware/src/Accelerometers/Accelerometers.cpp\"",
    "file": "C:/Eclipse/Firmware-3.6/RepRapFirmware/src/Accelerometers/Accelerometers.cpp"
  },
  {

This is the tools setup I am using:

where ArmGccPath is a build variable containing the path to the version of gcc that this workspace uses, for example:

The .cproject file is available at https://github.com/Duet3D/RepRapFirmware/blob/3.6-dev/.cproject. The make utility in use is the one provided by MSYS2.

[jonahgraham]

@Kummallinen / @alicetrifu can you have a look at this issue please?

I can't reproduce exactly what @dc42 has, but on Linux, creating a C project with a cross-compile toolchain leads me to a compile commands.json with:

"command": "\"/usr/bin/gcc\" arm-none-eabi- -O0 -g3 -Wall...

AFAICT if you don't have gcc on your PATH you get what @dc42 reports.

The error comes from an error introduced in #824 when full command lines were added. The assumption was that the ITool described the full toolname, but when using cross gcc, the IManagedCommandLineGenerator modifies the command by adding the prefix. i.e. ITool.getToolCommand returns gcc, but CrossCommandLineGenerator modifies it to be arm-none-eabi-gcc.

The problem can be seen here:

cdt/build/org.eclipse.cdt.managedbuilder.core/src/org/eclipse/cdt/managedbuilder/internal/core/jsoncdb/generator/CompilationDatabaseGenerator.java

Lines 232 to 234 in 7420b12

	String compilerName = CompilationDatabaseGenerator.getCompilerName(tool);
	String commandLine = cmdLInfo.getCommandLine();
	commandLine = commandLine.replace(compilerName, "").trim(); //$NON-NLS-1$

commandLine has the correct value, but not an absolute path. However compilerName has the non-prefixed value (e.g. just gcc) so the commandLine.replace call changes arm-none-eabi-gcc to arm-none-eabi-. The following lines then try to find the full path of gcc, instead of the prefixed arm-none-eabi-gcc leading to the wrong result