Here’s an actual piece of code that I’ve pulled out of a larger project. (Sorry, it’s the shortest one I can find that had a noticable speedup from prefetching.) This code performs a very large data transpose. This example uses the SSE prefetch instructions, which may be the same as the one that GCC emits. … Read more
It has been this way for a long time already. The “GCC” that came with 10.8 was really GCC front-end with LLVM back-end. The best way to get GCC is via Homebrew. After the one-line homebrew install command on the bottom of the linked page, you just need: $ brew install gcc49 Unlike macports, Homebrew … Read more
Debian / Ubuntu The problem is you likely only have the gcc for your current architecture and that’s 64bit. You need the 32bit support files. For that, you need to install them sudo apt install gcc-multilib
gcc -lsome_dynamic_lib code.c some_static_lib.a
Never try to set the compiler in the CMakeLists.txt file. See the CMake FAQ about how to use a different compiler: https://gitlab.kitware.com/cmake/community/wikis/FAQ#how-do-i-use-a-different-compiler (Note that you are attempting method #3 and the FAQ says “(avoid)”…) We recommend avoiding the “in the CMakeLists” technique because there are problems with it when a different compiler was used for … Read more
Let’s use the example code from the other question. Compile it, but tell gcc not to assemble: gcc -std=c99 -S -O2 test.c Now let’s look at the _atoi function in the resultant test.s file (gcc 4.0.1 on Mac OS 10.5): .text .align 4,0×90 _atoi: pushl %ebp testl %eax, %eax movl %esp, %ebp movl %eax, %ecx … Read more
As already pointed out elsewhere on this site, see this page: Auto-Dependency Generation In short, gcc can automatically create .d dependency files for you, which are mini makefile fragments containing the dependencies of the .c file you compiled. Every time you change the .c file and compile it, the .d file will be updated. Besides … Read more
The answer depends on the platform. On most platforms, if output from readelf –relocs foo.o | egrep ‘(GOT|PLT|JU?MP_SLOT)’ is empty, then either foo.o was not compiled with -fPIC, or foo.o doesn’t contain any code where -fPIC matters.
Yes, but you have to specify the language using the -x option: # Specify input file as stdin, language as C flex -t lexer.l | gcc -o lexer.o -xc –
Yes. From documentation v4.1.2 From documentation latest always_inline Generally, functions are not inlined unless optimization is specified. For functions declared inline, this attribute inlines the function even if no optimization level was specified.