Qt Creator Clang Code Model: Difference between revisions

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Linux/Mac:
Linux/Mac:
  export QT_LOGGING_RULES=qtc.clang*=true
  export QT_LOGGING_RULES=qtc.clang*=true
export LIBCLANG_TIMING=1
  ./qtcreator
  ./qtcreator


Windows (start [https://technet.microsoft.com/en-us/sysinternals/debugview.aspx DebugView] in advance to see the output):
Windows (start [https://technet.microsoft.com/en-us/sysinternals/debugview.aspx DebugView] in advance to see the output):
  set QT_LOGGING_RULES=qtc.clang*=true
  set QT_LOGGING_RULES=qtc.clang*=true
set LIBCLANG_TIMING=1
  qtcreator.exe
  qtcreator.exe


The debugging output contains among others:
This will create way too much output. But since the lines are prefixed with the rule that generated them, you can easily adapt your settings to what you are actually interested in.
* The IPC messages send/received
* Output of libclang while parsing


=== Internal command line ===  
=== Compiler command lines for the code model context ===  
The debugging output from above will contain all the command line options that are passed on to libclang, which is enough for most cases.
The file <build dir>/.qtc_clangd/compile_commands.json contains the exact command lines that clangd uses to parse the files in the project.


However, to see also the resulting internal command line of libclang run:
# Restart Qt Creator with QTC_CLANG_NO_DIAGNOSTIC_CHECK=1 (>= Qt Creator 4.5)
# Switch to projects mode and there to the "Clang Code Model"
# Copy some warning configuration by clicking on "Copy...", give it a name like "Debug"
# Replace all the options from the copied configuration with "-###"
# Close and re-open the editor document - the new debugging output will contain also the internal command line
Note that libclang/clangbackend will crash afterwards, so do not forget to switch back to a sane warning configuration.
== Related Environment Variables ==
== Related Environment Variables ==
=== Build related ===
* QTC_NO_CLANG_LIBTOOLING - Do not build against Clang's C++ libs; the ClangRefactoring plugin won't be build.
=== Run time related ===
=== Run time related ===
* LIBCLANG_TIMING - Timings from libclang for parse / reparse / preamble generation / completion.
* QTC_CLANG_USE_TOOLCHAIN_MACROS - Uses also the toolchain macros for code model
* QTC_CLANG_NO_DIAGNOSTIC_CHECK - Avoid validation of warning configuration (>= Qt Creator 4.5)
* QTC_CLANG_CMD_OPTIONS_BLACKLIST - Semicolon sepparated list of compiler command line options not to be passed to code model
* QTC_CLANG_NO_SUPPORTIVE_TRANSLATIONUNIT - Use only one translation unit per document.
* QTC_CLANG_NO_ALIVE_TIMER - Simplifies debugging in certain cases.
* QTC_CLANG_FORCE_VERBOSE_ALIVE - Simplifies debugging in certain cases.


== Libclang ==
== clangd ==
libclang is used inside clangbackend to provide code model features
clangd is used via the language server protocol to provide code model features


=== Builds ===
=== Builds ===
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Currently libclang is built with optimized MinGW compiler for all Qt Creator versions. More information about Windows builds: [[Build libclang on Windows]]
Currently libclang is built with optimized MinGW compiler for all Qt Creator versions. More information about Windows builds: [[Build libclang on Windows]]
=== Minimal libclang installation that Qt Creator can use ===
The following targets are sufficient for this:
install-libclang install-libclang-headers install-clang-headers install-llvm-config
== Clang Plugins ==
Clang plugins support is not yet in QtCreator but it's definitely on the way. There are already private builds that support Tidy and Clazy.
Plugins usage significantly reduces libclang performance:
=== Clazy ===
with default settings (level1) adds '''50%''' to the parse/re-parse time, level0 adds only '''25%'''
=== Clang Tidy ===
with -checks='-*,clang-diagnostic-*,llvm-*,misc-*,-misc-unused-parameters,readability-identifier-naming' adds '''200%''' to the original libclang parse/re-parse times
Because of that we want to make plugins options configurable when they appear in Qt Creator to give user the control over the amount of warnings/performance balance that one requires.

Latest revision as of 14:27, 20 May 2022

Documentation: http://doc.qt.io/qtcreator/creator-clang-codemodel.html

Debugging

With the following invocation debugging output will be generated:

Linux/Mac: 

export QT_LOGGING_RULES=qtc.clang*=true
./qtcreator

Windows (start DebugView in advance to see the output): 

set QT_LOGGING_RULES=qtc.clang*=true
qtcreator.exe

This will create way too much output. But since the lines are prefixed with the rule that generated them, you can easily adapt your settings to what you are actually interested in.

Compiler command lines for the code model context

The file <build dir>/.qtc_clangd/compile_commands.json contains the exact command lines that clangd uses to parse the files in the project.

Related Environment Variables

Run time related

  • QTC_CLANG_USE_TOOLCHAIN_MACROS - Uses also the toolchain macros for code model
  • QTC_CLANG_CMD_OPTIONS_BLACKLIST - Semicolon sepparated list of compiler command line options not to be passed to code model

clangd

clangd is used via the language server protocol to provide code model features

Builds

Linux and Mac:

libclang is built with the same compilers as Qt Creator ("Clang 7.0 (Apple)" for macOS, and GCC 5.3 from RHEL (which turns on old ABI compatibility with _GLIBCXX_USE_CXX11_ABI=0 by default) on Linux)

Windows:

Currently libclang is built with optimized MinGW compiler for all Qt Creator versions. More information about Windows builds: Build libclang on Windows

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