Clang
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Clang on Windows
LLVM-MinGW
- Get packages from https://github.com/mstorsjo/llvm-mingw
The best port of LLVM/Clang on Windows I tried.
- No dependency on Visual Studio.
- Support 32-bit and 64-bit targets.
- Support sanitizers (ASAN, UBSAN).
MSYS2
MSYS2 now provides clang 9.0 packages.
- No dependency on Visual Studio.
- Support 32-bit and 64-bit targets.
- But does not support sanitizers (ASAN, UBSAN).
Official LLVM
Packages from the official LLVM at http://releases.llvm.org/download.html.
- DEPEND on Visual Studio for linking
- Support 32-bit and 64-bit targets.
- (Maybe) support sanitizers (ASAN, UBSAN).
Tips
Get Stack Pointer
Use this macro [1]:
#define current_stack_pointer ({ \
register unsigned long esp asm("esp"); \
asm("" : "=r"(esp)); \
esp; \
})
Turn errors into warning
-Wno-error=foo Turn warning “foo” into an warning even if -Werror is specified.
Enable all warnings: -Weverything
-Weverything means enable all current and future warnings. See Better Apps with Clang's Weverything or Wall is a Lie!
Make deterministic / reproducible builds
Things to look at:
__DATE__and__TIME__. On clang, we can doexport ZERO_AR_DATE=1.__FILE__. On clang, we can add a flag-ffile-prefix-map=/some/local/build/path=..__LINE__.- some randomness introduced by compiler: Use flag
-frandom-seed=0x${checksum}.
Some script I used:
ag -l __LINE__ | xargs sed -ri 's/__LINE__/1/g'
make NODEBUG=1 some.elf # Optional, but ideally build without flag -g
strip --strip-all some.elf
sha256sum some.elf
Troubleshoot
iostream not found
This is a funny one. Simple Hello, World program that fails with an
#include <iostream>
using namespace std;
int main() {
cout << "Hello, World" << endl;
return 0;
}
clang++ main.cpp
# main.cpp:1:10: fatal error: 'iostream' file not found
# #include <iostream>
# ^~~~~~~~~~
# 1 error generated.
Luckily StackOverflow comes to the rescue.
The problem is that we have several gcc/g++ installation, and the one selected by clang doesn't have the c++ headers.
$ clang++ -v main.cpp
clang version 7.0.1-8 (tags/RELEASE_701/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/10
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/9
Candidate multilib: .;@m64
Selected multilib: .;@m64
"/usr/lib/llvm-7/bin/clang" -cc1 [...]
clang -cc1 version 7.0.1 based upon LLVM 7.0.1 default target x86_64-pc-linux-gnu
ignoring nonexistent directory "/usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/x86_64-linux-gnu"
ignoring nonexistent directory "/usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/backward"
ignoring nonexistent directory "/include"
ignoring duplicate directory "/usr/include/clang/7.0.1/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++
/usr/include/clang/7.0.1/include
/usr/local/include
/usr/include/x86_64-linux-gnu
/usr/include
End of search list.
main.cpp:1:10: fatal error: 'iostream' file not found
#include <iostream>
^~~~~~~~~~
1 error generated.
The simplest for us was to uninstall gcc-9. Another solution is to install g++-9. Also it seems that clang uses some kind of prioritization, so in fact reinstalling gcc-8/g++-8 may work as well.