omp.h file not found, and visual studio code can't found omp.h

[marianofernandezs]

Output of brew config

#include <omp.h> ## omp.h file not found
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char* argv[]){
int nthreads = 3;
int tid;
printf("Antes del fork\n");
omp_set_num_threads(nthreads);
#pragma omp parallel private(nthreads, tid)
{
tid = omp_get_thread_num();
printf("Ejecutando thread %d - ",tid);
if (tid >= 0 && tid < (omp_get_num_threads() / 2 )){
printf("Soy productor\n");
}
else{
printf("Soy consumidor\n");
}
if(tid == 0){
printf("SOY EL PRINCIPAL: num_threads %d \n",
omp_get_num_threads());
}
}
printf("Despues del join");
}

Output of brew doctor

id: library 'omp' not found
clang: error: linker command failed with exit code 1 (use -v to see invocation)

 *  The terminal process "/bin/zsh '-l', '-c', '/usr/local/opt/llvm/bin/clang -Xpreprocessor -fopenmp -lomp /Users/mariano/Downloads/c/programa.c -o /Users/mariano/Downloads/c/programa'" terminated with exit code: 1

Description of issue

hi, I installed llvm and libomp in my MacBook Pro 16 Late 2019, I have a problem with visual studio can't run and compile my code, and the terminal return this:

id: library 'omp' not found
clang: error: linker command failed with exit code 1 (use -v to see invocation)

• The terminal process "/bin/zsh '-l', '-c', '/usr/local/opt/llvm/bin/clang -Xpreprocessor -fopenmp -lomp /Users/mariano/Downloads/c/programa.c -o /Users/mariano/Downloads/c/programa'" terminated with exit code: 1

I need help, I tried to chatgpt help but didn't get the solution he gave me. I tried to configure task.json but it didn't work.
If you land here, I would appreciate it.

[ZhongRuoyu]

What's the output of brew info llvm?

[marianofernandezs]

lvm: stable 17.0.6 (bottled), HEAD [keg-only]
Next-gen compiler infrastructure
https://llvm.org/
/usr/local/Cellar/llvm/17.0.6_1 (7,207 files, 1.8GB)
Poured from bottle using the formulae.brew.sh API on 2024-03-24 at 23:52:48
From: https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/l/llvm.rb
License: Apache-2.0 with LLVM-exception
==> Dependencies
Build: cmake ✔, ninja ✔, swig ✔
Required: [email protected] ✔, z3 ✔, zstd ✔
==> Options
--HEAD
Install HEAD version
==> Caveats
To use the bundled libc++ please add the following LDFLAGS:
LDFLAGS="-L/usr/local/opt/llvm/lib/c++ -Wl,-rpath,/usr/local/opt/llvm/lib/c++"

llvm is keg-only, which means it was not symlinked into /usr/local,
because macOS already provides this software and installing another version in
parallel can cause all kinds of trouble.

If you need to have llvm first in your PATH, run:
echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"' >> ~/.zshrc

For compilers to find llvm you may need to set:
export LDFLAGS="-L/usr/local/opt/llvm/lib"
export CPPFLAGS="-I/usr/local/opt/llvm/include"
==> Analytics
install: 37,205 (30 days), 138,519 (90 days), 499,172 (365 days)
install-on-request: 15,214 (30 days), 60,132 (90 days), 311,780 (365 days)
build-error: 338 (30 days)

This is my output

[ZhongRuoyu]

-Xpreprocessor means its subsequent flag is passed to the preprocessor only, so the compiler driver is not passing the OpenMP-related ldflags to the linker. Removing the -Xpreprocessor flag should work.

[marianofernandezs]

Thanks, i don't work

[trinitronx]

Looks like tasks.json is correct for the keg-only include dirs for llvm. So compile via VSCode's "Tasks -> build" should work. If you just need libomp, then you have a choice of using brew install libomp for the standalone runtime lib, or brew install llvm if using the one from LLVM. For the libomp version, you can try adding this to the build task:

{
  "tasks": [
    {
      "args": [
        "-L/usr/local/opt/libomp/lib",
        "-I/usr/local/opt/libomp/include",
        "-lomp"
      ]
    }
  ]
}

Note that in VSCode, the IntelliSense warnings are coming from a different set of commands that VSCode runs in the background (usually clangd, clang-tidy, or oclint when using LLVM), which are not taking into account any specified args in tasks.json because they use separate configuration files. You will usually need to generate a compile_commands.json first for VSCode with clangd, and most other linting extensions that use this compilation database to find the same includes and give the right IntelliSense warnings & output in the "Problems" tab. For use with llvm & clangd, I've had some luck using the intercept-build tool from scan-build which can be installed via pip as a Python module. This command can then be prefixed to your compile command in tasks.json (e.g. intercept-build --append ...make command + args here...). Alternatively, or in addition to the compile_commands.json, you can try using a .clangd file to configure the global include args for clangd to find:

.clangd:

CompileFlags:
    CompilationDatabase: "."
    Add:
    - "-Iexample/include"
    - "-Imore-includes/include"