gcccmakeclangscan-build

Clang's 'scan-build' utilite does not work with 'make'

I'm trying to statically analyze my code via Clang's static code analyzer tool scan-build and when I run the code with scan-build g++ command, it provides me a bug report, but when I'm trying to do same thing with CMake and the scan-build make command, it tells me that no bugs were found.

I've already tried to substitute CC and CXX variables by bash export command, used --use_cc and --use_c++ flags and built separate targets using scan-build make TARGET. All of this did not lead me to the correct solution and I'm afraid that scan-build could not work with CMake/make.

Here is a simple example.

CMakeLists.txt

cmake_minimum_required(VERSION 3.10)

set(CMAKE_C_COMPILER    "usr/bin/clang")
set(CMAKE_CXX_COMPILER  "usr/bin/clang++")
set(CMAKE_AR            "usr/bin/llvm-ar")
set(CMAKE_LINKER        "usr/bin/llvm-ld")
set(CMAKE_NM            "usr/bin/llvm-nm")
set(CMAKE_OBJDUMP       "usr/bin/llvm-objdump")
set(CMAKE_RANLIB        "usr/bin/llvm-ranlib")

project(scan-build-test)
add_executable(${PROJECT_NAME} main.cpp)

main.cpp

#include <iostream>

int main()
{
    int *a;
    std::cout << a << std::endl;
}

Current behavior g++:

scan-build g++ main.cpp -o main
scan-build: Using 'usr/bin/clang-8' for static analysis main.cpp:6:2: warning: 1st function call argument is an uninitialized value
    std::cout << a << std::endl;
    ^~~~~~~~~~~~~~
1 warning generated.
scan-build: 1 bug found.
scan-build: Run 'scan-view /tmp/scan-build-2019-05-30-134021-30676-1' to examine bug reports.`

Current behavior CMake & make:

cmake .
scan-build make
scan-build: Using 'usr/bin/clang-8' for static analysis
[ 50%] Building CXX object CMakeFiles/scan-build-test.dir/main.cpp.o
[100%] Linking CXX executable scan-build-test
[100%] Built target scan-build-test
scan-build: Removing directory '/tmp/scan-build-2019-05-30-134302-30720-1' because it contains no reports.
scan-build: No bugs found.
Solution

  • All static analysis (and other source code related) instruments for C/C++ need to replicate the compilation process for each source file in your project. In order to get everything right, they need to have all the compilation options (like macro definitions and include directories) that were used during the real compilation.

    There are a few ways to do it. Without getting into much details about other approaches, here's how scan-build does it. It substitutes the real compiler with its wrapper executable, receives all the compiler commands from the build system, does its job and forwards all the same options to the real compiler.

    That's why direct SET commands for compiler in your CMakeLists.txt file prevented scan-build from doing its trick. It will work with both gcc and clang, but you should not hardcode them and use CC and CXX environment variables instead.