I have built clang 3.6 from source and followed the rather straightforward instruction on the page and installed ninja, which I confirmed can build clang-format.
My question is quite simply how to pass some flags so I can get debug symbols because I do not want to do my work (modifying clang-format) using disassembly throughout.
This can be through the standard build (which uses CMake) or ninja.
I've faced similar issue recently (I wanted to debug clang's code itself). Turned out that you need to explicitly specify -DCMAKE_BUILD_TYPE=Debug when you run CMake to generate Ninja or standard makefiles.
BTW, be careful: with this Debug option ld "ate" about 4G of my RAM to link clang binary...
Related
I'm trying to compile CMake using a non-default GCC installed in /usr/local/gcc530, on Solaris 2.11.
I have LD_LIBRARY_PATH=/usr/local/gcc530/lib/sparcv9
Bootstrap proceeds fine, bootstrapped cmake successfully compiles various object files, but when it tries to link the real cmake (and other executables), I get pages of "undefined reference" errors to various standard library functions, because, as running the link command manually with -Wl,-verbose shows, the linker links with /usr/lib/64/libstdc++.so of the system default, much older GCC.
This is because apparently CMake tries to find curses/ncurses libraries (even if I tell it BUILD_CursesDialog:BOOL=OFF), finds them in /usr/lib/64, and adds -L/usr/lib/64 to build/Source/CMakeFiles/cmake.dir/link.txt, which causes the linker to use libstdc++.so from there, and not my actual GCC's own.
I found a workaround: I can get the path to proper libraries from $CC -m64 -print-file-name=libstdc++.so then put it with -L into LDFLAGS when running ./configure, and all works well then.
Is there a less hacky way? It's really weird that I can't tell GCC to prioritize its own libraries.
Also, is there some way to have CMake explain where different parts of a resulting command line came from?
I know how to build gcc from source, what I still have to figure out is what are the exact environmental variables used by gcc when configure and building gcc itself, I'm actually trying to build the compiler from source using another version of gcc with different ABI.
Any idea on how to get this kind of information beside "try to grep all the variable that starts with $ inside all makefiles and configuration files" ?
You can see a list of Environment Variables Affecting GCC.
To create a completly independent gcc with a new toolset, have a look at LFS, they explain how to build gcc from an existing OS for a future OS.
There is also a page about building gcc, which talks about BOOT_CFLAGS='-O' and CFLAGS_FOR_TARGET and STAGE1_TFLAGS and BUILD_CONFIG. There is also some additional variables for cross-compiling and ada compiler.
Using MinGW and CMake I've compiled LLVM, Clang and Compiler-RT both via SVN or using the released source code (3.2).
I've modified InitHeaderSearch.cpp (in tools/clang/lib/frontend) to find GCC 4.7.2 headers.
I've set the compile options to Release and disabled assertions.
Clang seems to work properly, but it takes 4-5 seconds to start: even typing "clang --version" in the console does this. Compiling a projects takes a lot of time.
What am I missing? I've used rubenvb's old MinGW+Clang build (GCC 4.6), and it didn't have this problem. Is there any compilation flag I need to use?
This issue is discussed here http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-April/020651.html
AFAIK problem is caused by large relocation table and inefficient MinGW implementation (http://sourceforge.net/p/mingw/bugs/1747/).
Adding -static flag to linker flags should resolve this issue. You should invoke cmake with
-DCMAKE_EXE_LINKER_FLAGS=-static -DCMAKE_MODULE_LINKER_FLAGS=-static
According to LLVM's Getting Started (Windows) site:
... Clang can be used to emit bitcode, directly emit object files or even linked executables using Visual Studio’s link.exe.
Why is the use of Link.exe on Windows necessary? And, for that matter, what is used on Mac/Linux? Further down it says:
Compile the program to object code using the LLC code generator:
C:\..> llc -filetype=obj hello.bc
Link to binary using Microsoft link:
C:\..> link hello.obj -defaultlib:libcmt
Why can't LLC perform that last step? LLI seems to work fine so I assume that it interoperates with link.exe somehow under the hood - why can't LLC?
Because no one has written a linker for LLVM.
There is a project to do so (called, unimaginatively lld) but it's not ready yet.
See http://lld.llvm.org for more details.
On the mac, people use Apple's linker, ld.
On Linux, most people use the gnu linker, usually (also) named ld
Try MinGW-W64's ld. I've been using it with llvm's clang instead of VS tools that I used for building clang in the first place.
we here use -Werror=unused-but-set-variable gcc compiler option while building our code. Apparently the people using gcc4.5 can build it "even though" there are variables which are set but not used afterwards. But I using gcc4.6 cannot build the code. Is that particular gcc option not implemented in gcc4.5?
thanks in advance
The GCC 4.6 warnings are improved w.r.t. to those produced by GCC 4.5. But you could just use -Wunused-but-set-variable to get warnings, not errors, and more importantly correct your source code (perhaps by removing that useless variable).