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[clang-tidy] Updated docs on testing clang-tidy checks. 

llvm-svn: 261622
This commit is contained in:
Alexander Kornienko 2016-02-23 09:30:20 +00:00
parent 2a62b3c244
commit 6bb4b88216
1 changed files with 20 additions and 2 deletions
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22
clang-tools-extra/docs/clang-tidy/index.rst
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@ -546,11 +546,12 @@ It's advised to make the checks as specific as possible to avoid checks matching
to incorrect parts of the input. Use ``[[@LINE+X]]``/``[[@LINE-X]]``
substitutions and distinct function and variable names in the test code.
Here's an example of a test using the ``check_clang_tidy.py`` script:
Here's an example of a test using the ``check_clang_tidy.py`` script (the full
source code is at `test/clang-tidy/google-readability-casting.cpp`_):
.. code-block:: bash
// RUN: %python %S/check_clang_tidy.py %s google-readability-casting %t
// RUN: %check_clang_tidy %s google-readability-casting %t
void f(int a) {
int b = (int)a;
@ -558,8 +559,25 @@ Here's an example of a test using the ``check_clang_tidy.py`` script:
// CHECK-FIXES: int b = a;
}
There are many dark corners in the C++ language, and it may be difficult to make
your check work perfectly in all cases, especially if it issues fixit hints. The
most frequent pitfalls are macros and templates:
1. code written in a macro body/template definition may have a different meaning
depending on the macro expansion/template instantiation;
2. multiple macro expansions/template instantiations may result in the same code
being inspected by the check multiple times (possibly, with different
meanings, see 1), and the same warning (or a slightly different one) may be
issued by the check multipe times; clang-tidy will deduplicate _identical_
warnings, but if the warnings are slightly different, all of them will be
shown to the user (and used for applying fixes, if any);
3. making replacements to a macro body/template definition may be fine for some
macro expansions/template instantiations, but easily break some other
expansions/instantiations.
.. _lit: http://llvm.org/docs/CommandGuide/lit.html
.. _FileCheck: http://llvm.org/docs/CommandGuide/FileCheck.html
.. _test/clang-tidy/google-readability-casting.cpp: http://reviews.llvm.org/diffusion/L/browse/clang-tools-extra/trunk/test/clang-tidy/google-readability-casting.cpp
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