Mirror of forum.nim-lang.org

13257 :: How to access c preprocessor definitions, esp. with __underscores?

• dwhall256 (orginal) [2025-07-26T17:32:36+02:00] view original

  Context: embedded systems.

  The greater goal is to create a Nim module that is able to determine the ARM architecture of the processor selected by the programmer-user of my module. The module user selects a compiler (gcc or clang) and passes C arguments on the build command line that selects a particular architecture variant.

  Step 1: I'm using when defined(clang): ... elif defined(gcc): ... to determine the compiler. I'm not supporting other compilers at this time.

  Step 2: My current idea is within the compiler conditional to access compiler-specific c preprocessor definitions to determine the ARM architecture.

  Can someone give a suggestion how to do this? Or a better path to obtain this information at compile time?

---

• dwhall256 (orginal) [2025-07-26T19:28:17+02:00] view original

  I've done this:

  
  const ARM_ARCH {.intdefine: "__ARM_ARCH".} = 0
  Run

  which is a start. But for another compiler, I need to figure out the number when it is embedded in the definition's name, as in __ARM_ARCH_'V'__

---

• demotomohiro (orginal) [2025-07-26T19:59:33+02:00] view original

  
  let gnuc {.importc: "__GNUC__", nodecl.}: int
  echo gnuc
  Run

  But you cannot access C preprocessor defines at compime time of Nim.

---