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ClickHouse/cmake/warnings.cmake
Robert Schulze 5a4f21c50f
Support for Clang Thread Safety Analysis (TSA) 
- TSA is a static analyzer build by Google which finds race conditions
  and deadlocks at compile time.

- It works by associating a shared member variable with a
  synchronization primitive that protects it. The compiler can then
  check at each access if proper locking happened before. A good
  introduction are [0] and [1].

- TSA requires some help by the programmer via annotations. Luckily,
  LLVM's libcxx already has annotations for std::mutex, std::lock_guard,
  std::shared_mutex and std::scoped_lock. This commit enables them
  (--> contrib/libcxx-cmake/CMakeLists.txt).

- Further, this commit adds convenience macros for the low-level
  annotations for use in ClickHouse (--> base/defines.h). For
  demonstration, they are leveraged in a few places.

- As we compile with "-Wall -Wextra -Weverything", the required compiler
  flag "-Wthread-safety-analysis" was already enabled. Negative checks
  are an experimental feature of TSA and disabled
  (--> cmake/warnings.cmake). Compile times did not increase noticeably.

- TSA is used in a few places with simple locking. I tried TSA also
  where locking is more complex. The problem was usually that it is
  unclear which data is protected by which lock :-(. But there was
  definitely some weird code where locking looked broken. So there is
  some potential to find bugs.

*** Limitations of TSA besides the ones listed in [1]:

- The programmer needs to know which lock protects which piece of shared
  data. This is not always easy for large classes.

- Two synchronization primitives used in ClickHouse are not annotated in
  libcxx:
  (1) std::unique_lock: A releaseable lock handle often together with
      std::condition_variable, e.g. in solve producer-consumer problems.
  (2) std::recursive_mutex: A re-entrant mutex variant. Its usage can be
      considered a design flaw + typically it is slower than a standard
      mutex. In this commit, one std::recursive_mutex was converted to
      std::mutex and annotated with TSA.

- For free-standing functions (e.g. helper functions) which are passed
  shared data members, it can be tricky to specify the associated lock.
  This is because the annotations use the normal C++ rules for symbol
  resolution.

[0] https://clang.llvm.org/docs/ThreadSafetyAnalysis.html
[1] https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/42958.pdf
2022-06-20 16:13:25 +02:00

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# Our principle is to enable as many warnings as possible and always do it with "warnings as errors" flag.
#
# But it comes with some cost:
# - we have to disable some warnings in 3rd party libraries (they are located in "contrib" directory)
# - we have to include headers of these libraries as -isystem to avoid warnings from headers
# (this is the same behaviour as if these libraries were located in /usr/include)
# - sometimes warnings from 3rd party libraries may come from macro substitutions in our code
# and we have to wrap them with #pragma GCC/clang diagnostic ignored
set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra")
# Control maximum size of stack frames. It can be important if the code is run in fibers with small stack size.
# Only in release build because debug has too large stack frames.
if ((NOT CMAKE_BUILD_TYPE_UC STREQUAL "DEBUG") AND (NOT SANITIZE) AND (NOT CMAKE_CXX_COMPILER_ID MATCHES "AppleClang"))
add_warning(frame-larger-than=65536)
endif ()
if (COMPILER_CLANG)
# Add some warnings that are not available even with -Wall -Wextra -Wpedantic.
# We want to get everything out of the compiler for code quality.
add_warning(everything)
add_warning(pedantic)
no_warning(vla-extension)
no_warning(zero-length-array)
no_warning(c11-extensions)
no_warning(unused-command-line-argument)
no_warning(c++98-compat-pedantic)
no_warning(c++98-compat)
no_warning(c99-extensions)
no_warning(conversion)
no_warning(ctad-maybe-unsupported) # clang 9+, linux-only
no_warning(deprecated-dynamic-exception-spec)
no_warning(disabled-macro-expansion)
no_warning(documentation-unknown-command)
no_warning(double-promotion)
no_warning(exit-time-destructors)
no_warning(float-equal)
no_warning(global-constructors)
no_warning(missing-prototypes)
no_warning(missing-variable-declarations)
no_warning(nested-anon-types)
no_warning(packed)
no_warning(padded)
no_warning(return-std-move-in-c++11) # clang 7+
no_warning(shift-sign-overflow)
no_warning(sign-conversion)
no_warning(switch-enum)
no_warning(undefined-func-template)
no_warning(unused-template)
no_warning(vla)
no_warning(weak-template-vtables)
no_warning(weak-vtables)
no_warning(thread-safety-negative) # experimental flag, too many false positives
# TODO Enable conversion, sign-conversion, double-promotion warnings.
elseif (COMPILER_GCC)
# Add compiler options only to c++ compiler
function(add_cxx_compile_options option)
add_compile_options("$<$<STREQUAL:$<TARGET_PROPERTY:LINKER_LANGUAGE>,CXX>:${option}>")
endfunction()
# Warn about boolean expression compared with an integer value different from true/false
add_cxx_compile_options(-Wbool-compare)
# Warn whenever a pointer is cast such that the required alignment of the target is increased.
add_cxx_compile_options(-Wcast-align)
# Warn whenever a pointer is cast so as to remove a type qualifier from the target type.
add_cxx_compile_options(-Wcast-qual)
# Warn when deleting a pointer to incomplete type, which may cause undefined behavior at runtime
add_cxx_compile_options(-Wdelete-incomplete)
# Warn if a requested optimization pass is disabled. Code is too big or too complex
add_cxx_compile_options(-Wdisabled-optimization)
# Warn about duplicated conditions in an if-else-if chain
add_cxx_compile_options(-Wduplicated-cond)
# Warn about a comparison between values of different enumerated types
add_cxx_compile_options(-Wenum-compare)
# Warn about uninitialized variables that are initialized with themselves
add_cxx_compile_options(-Winit-self)
# Warn about logical not used on the left hand side operand of a comparison
add_cxx_compile_options(-Wlogical-not-parentheses)
# Warn about suspicious uses of logical operators in expressions
add_cxx_compile_options(-Wlogical-op)
# Warn if there exists a path from the function entry to a use of the variable that is uninitialized.
add_cxx_compile_options(-Wmaybe-uninitialized)
# Warn when the indentation of the code does not reflect the block structure
add_cxx_compile_options(-Wmisleading-indentation)
# Warn if a global function is defined without a previous declaration - disabled because of build times
# add_cxx_compile_options(-Wmissing-declarations)
# Warn if a user-supplied include directory does not exist
add_cxx_compile_options(-Wmissing-include-dirs)
# Obvious
add_cxx_compile_options(-Wnon-virtual-dtor)
# Obvious
add_cxx_compile_options(-Wno-return-local-addr)
# This warning is disabled due to false positives if compiled with libc++: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90037
#add_cxx_compile_options(-Wnull-dereference)
# Obvious
add_cxx_compile_options(-Wodr)
# Obvious
add_cxx_compile_options(-Wold-style-cast)
# Warn when a function declaration hides virtual functions from a base class
# add_cxx_compile_options(-Woverloaded-virtual)
# Warn about placement new expressions with undefined behavior
add_cxx_compile_options(-Wplacement-new=2)
# Warn about anything that depends on the “size of” a function type or of void
add_cxx_compile_options(-Wpointer-arith)
# Warn if anything is declared more than once in the same scope
add_cxx_compile_options(-Wredundant-decls)
# Member initialization reordering
add_cxx_compile_options(-Wreorder)
# Obvious
add_cxx_compile_options(-Wshadow)
# Warn if left shifting a negative value
add_cxx_compile_options(-Wshift-negative-value)
# Warn about a definition of an unsized deallocation function
add_cxx_compile_options(-Wsized-deallocation)
# Warn when the sizeof operator is applied to a parameter that is declared as an array in a function definition
add_cxx_compile_options(-Wsizeof-array-argument)
# Warn for suspicious length parameters to certain string and memory built-in functions if the argument uses sizeof
add_cxx_compile_options(-Wsizeof-pointer-memaccess)
# Warn about overriding virtual functions that are not marked with the override keyword
add_cxx_compile_options(-Wsuggest-override)
# Warn whenever a switch statement has an index of boolean type and the case values are outside the range of a boolean type
add_cxx_compile_options(-Wswitch-bool)
# Warn if a self-comparison always evaluates to true or false
add_cxx_compile_options(-Wtautological-compare)
# Warn about trampolines generated for pointers to nested functions
add_cxx_compile_options(-Wtrampolines)
# Obvious
add_cxx_compile_options(-Wunused)
add_cxx_compile_options(-Wundef)
# Warn if vector operation is not implemented via SIMD capabilities of the architecture
add_cxx_compile_options(-Wvector-operation-performance)
# Warn when a literal 0 is used as null pointer constant.
add_cxx_compile_options(-Wzero-as-null-pointer-constant)
# The following warnings are generally useful but had to be disabled because of compiler bugs with older GCCs.
# XXX: We should try again on more recent GCCs (--> see CMake variable GCC_MINIMUM_VERSION).
# gcc10 stuck with this option while compiling GatherUtils code, anyway there are builds with clang that will warn
add_cxx_compile_options(-Wno-sequence-point)
# gcc10 false positive with this warning in MergeTreePartition.cpp
# inlined from 'void writeHexByteLowercase(UInt8, void*)' at ../src/Common/hex.h:39:11,
# inlined from 'DB::String DB::MergeTreePartition::getID(const DB::Block&) const' at ../src/Storages/MergeTree/MergeTreePartition.cpp:85:30:
# ../contrib/libc-headers/x86_64-linux-gnu/bits/string_fortified.h:34:33: error: writing 2 bytes into a region of size 0 [-Werror=stringop-overflow=]
# 34 | return __builtin___memcpy_chk (__dest, __src, __len, __bos0 (__dest));
# For some reason (bug in gcc?) macro 'GCC diagnostic ignored "-Wstringop-overflow"' doesn't help.
add_cxx_compile_options(-Wno-stringop-overflow)
# reinterpretAs.cpp:182:31: error: ‘void* memcpy(void*, const void*, size_t)’ copying an object of non-trivial type
# ‘using ToFieldType = using FieldType = using UUID = struct StrongTypedef<wide::integer<128, unsigned int>, DB::UUIDTag>’
# {aka ‘struct StrongTypedef<wide::integer<128, unsigned int>, DB::UUIDTag>’} from an array of ‘const char8_t’
add_cxx_compile_options(-Wno-error=class-memaccess)
# Maybe false positive...
# In file included from /home/jakalletti/ClickHouse/ClickHouse/contrib/libcxx/include/memory:673,
# In function ‘void std::__1::__libcpp_operator_delete(_Args ...) [with _Args = {void*, long unsigned int}]’,
# inlined from ‘void std::__1::__do_deallocate_handle_size(void*, size_t, _Args ...) [with _Args = {}]’ at /home/jakalletti/ClickHouse/ClickHouse/contrib/libcxx/include/new:271:34,
# inlined from ‘void std::__1::__libcpp_deallocate(void*, size_t, size_t)’ at /home/jakalletti/ClickHouse/ClickHouse/contrib/libcxx/include/new:285:41,
# inlined from ‘constexpr void std::__1::allocator<_Tp>::deallocate(_Tp*, size_t) [with _Tp = char]’ at /home/jakalletti/ClickHouse/ClickHouse/contrib/libcxx/include/memory:849:39,
# inlined from ‘static constexpr void std::__1::allocator_traits<_Alloc>::deallocate(std::__1::allocator_traits<_Alloc>::allocator_type&, std::__1::allocator_traits<_Alloc>::pointer, std::__1::allocator_traits<_Alloc>::size_type) [with _Alloc = std::__1::allocator<char>]’ at /home/jakalletti/ClickHouse/ClickHouse/contrib/libcxx/include/__memory/allocator_traits.h:476:24,
# inlined from ‘std::__1::basic_string<_CharT, _Traits, _Allocator>::~basic_string() [with _CharT = char; _Traits = std::__1::char_traits<char>; _Allocator = std::__1::allocator<char>]’ at /home/jakalletti/ClickHouse/ClickHouse/contrib/libcxx/include/string:2219:35,
# inlined from ‘std::__1::basic_string<_CharT, _Traits, _Allocator>::~basic_string() [with _CharT = char; _Traits = std::__1::char_traits<char>; _Allocator = std::__1::allocator<char>]’ at /home/jakalletti/ClickHouse/ClickHouse/contrib/libcxx/include/string:2213:1,
# inlined from ‘DB::JSONBuilder::JSONMap::Pair::~Pair()’ at /home/jakalletti/ClickHouse/ClickHouse/src/Common/JSONBuilder.h:90:12,
# inlined from ‘void DB::JSONBuilder::JSONMap::add(std::__1::string, DB::JSONBuilder::ItemPtr)’ at /home/jakalletti/ClickHouse/ClickHouse/src/Common/JSONBuilder.h:97:68,
# inlined from ‘virtual void DB::ExpressionStep::describeActions(DB::JSONBuilder::JSONMap&) const’ at /home/jakalletti/ClickHouse/ClickHouse/src/Processors/QueryPlan/ExpressionStep.cpp:102:12:
# /home/jakalletti/ClickHouse/ClickHouse/contrib/libcxx/include/new:247:20: error: ‘void operator delete(void*, size_t)’ called on a pointer to an unallocated object ‘7598543875853023301’ [-Werror=free-nonheap-object]
add_cxx_compile_options(-Wno-error=free-nonheap-object)
# AggregateFunctionAvg.h:203:100: error: ‘this’ pointer is null [-Werror=nonnull]
add_cxx_compile_options(-Wno-error=nonnull)
endif ()
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