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_ENABLE_CLANG_LIBTOOLING - Build against Clang's C++ libs; the ClangFormat and ClangRefactoring plugin and dependencies will 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_ENABLE_STACKTRACES - For debugging. Enables the clang stack trace printer on a crash. Might deadlock clangbackend.
* QTC_CLANG_CMD_OPTIONS_BLACKLIST - Semicolon sepparated list of compiler command line options not to be passed to code model
* QTC_CLANG_NO_DIAGNOSTIC_CHECK - Avoid validation of warning configuration (>= Qt Creator 4.5)
* 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 ===
Line 54: Line 35:


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 already in last QtCreator release (4.6).
ClangTidy can be hardly transformed into dynamic plug-in (at least on Windows) and does not support plugins as a standalone tool. Therefore ClangTidy and Clazy are linked statically into libclang and clang driver (last one is in progress) in our custom clang builds.
Plugins usage significantly affects libclang performance so set up your settings (Tools->Options->C++->Code Model->Clang Plugins) wisely:
=== Clazy ===
level1 adds '''50%''' to the parse/re-parse time, level0 adds only '''25%'''
=== Clang Tidy ===
clang-diagnostic-*,llvm-*,misc-* add '''200%''' to the original libclang parse/re-parse times
== Backport candidates for Qt Creator 4.7 ==
== Backport candidates for Qt Creator 4.6 ==
Qt Creator 4.6 will ship with LLVM/Clang 5.
The following changes from LLVMt/Clang trunk might be worthwhile to backport.
'''Crash / Parsing'''
[Sema] Fix crash in unused-lambda-capture warning for VLAs
https://reviews.llvm.org/D41016
'''<s>Crash / Completion</s> (excluded because it leads to crashes in clang tests)'''
<s>Fixed a crash in code completion.</s>
[https://reviews.llvm.org/D37382 <s>https://reviews.llvm.org/D37382</s>]
Fixes crash when requesting completion at e.g. int (*foo(int a))(flo<CURSOR>
'''Crash / Completion'''
[Lex] Fix crash on code completion in comment in included file.
https://reviews.llvm.org/D41688
'''Crash / Static Analyzer'''
[analyzer] Fix a crash on C++17 AST for non-trivial construction into a trivial brace initializer.
https://reviews.llvm.org/D40841
'''Crash / Reparse,  MSVC 15.5 specific'''
Correctly handle line table entries without filenames during AST serialization
Fixes crash during a reparse.
https://reviews.llvm.org/D40746
'''[PCH] Serialize skipped preprocessor ranges'''
This fixes, for example, libclang's clang_getSkippedRanges returning zero ranges after reparsing a translation unit.
https://reviews.llvm.org/D20124
Affects highlighting of preprocessor ranges.
'''Minor / AST Access'''
[libclang] Fix cursors for in-class initializer of field declarations
https://reviews.llvm.org/D40027
https://bugs.llvm.org/show_bug.cgi?id=33745
Fixes AST access to initializers of class members. Affects mostly semantic highlighting and highlighting of local uses.
'''Minor / AST Access'''
[libclang] Fix cursors for functions with trailing return type
https://reviews.llvm.org/D40561
'''Minor / AST properties'''
[libclang] Add support for checking abstractness of records
https://reviews.llvm.org/D40072
Would need https://codereview.qt-project.org/#/c/211497/ on Qt Creator side.
'''Improves Tooltips'''
[DeclPrinter] Honor TerseOutput for constructors
https://reviews.llvm.org/D39957
Avoids printing member initialization list and body for constructor.
'''Fix utf8 specific highlighting issues'''
[libclang] Add function to get the buffer for a file
https://reviews.llvm.org/rL319881
Together with https://codereview.qt-project.org/#/c/212972/ fixes highlighting
'''Fix MSVC related highlighting issues'''
[libclang] Only mark CXCursors for explicit attributes with a type
Some classes have totally broken highlighting (like classes inside texteditor.cpp)
https://reviews.llvm.org/D38615
'''Fix templated type alias completion when using global completion cache'''
Fixes completion involving templated type alias.
https://reviews.llvm.org/D35355 (with slight update)
'''Fix overloaded static functions in SemaCodeComplete'''
Happens when static function is accessed via the class variable.
That leads to incorrect overloads number because the variable is considered as the first argument.
https://reviews.llvm.org/D36390
'''Fix overloaded static functions for templates'''
Apply almost the same fix as D36390 but for templates
https://reviews.llvm.org/D43453

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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