CFLAGS, CCFLAGS, CXXFLAGS – what exactly do these variables control?

by

As you noticed, these are Makefile {macros or variables}, not compiler options. They implement a set of conventions. (Macros is an old name for them, still used by some. GNU make doc calls them variables.)

The only reason that the names matter is the default make rules, visible via make -p, which use some of them.

If you write all your own rules, you get to pick all your own macro names.

In a vanilla gnu make, there’s no such thing as CCFLAGS. There are CFLAGS, CPPFLAGS, and CXXFLAGS. CFLAGS for the C compiler, CXXFLAGS for C++, and CPPFLAGS for both.

Why is CPPFLAGS in both? Conventionally, it’s the home of preprocessor flags (-D, -U) and both c and c++ use them. Now, the assumption that everyone wants the same define environment for c and c++ is perhaps questionable, but traditional.

P.S. As noted by James Moore, some projects use CPPFLAGS for flags to the C++ compiler, not flags to the C preprocessor. The Android NDK, for one huge example.

More Related Contents:

  1. How do I force make/GCC to show me the commands?
  2. gcc makefile error: “No rule to make target …”
  3. How can I have a Makefile automatically rebuild source files that include a modified header file? (In C/C++)
  4. How to set the LDFLAGS in CMakeLists.txt?
  5. make: *** [ ] Error 1 error [duplicate]
  6. Makefile removes object files for no reason
  7. Why does the order in which libraries are linked sometimes cause errors in GCC?
  8. CUDA incompatible with my gcc version
  9. How to install GCC piece by piece with GMP, MPFR, MPC, ELF, without shared libraries?
  10. How to see which flags -march=native will activate?
  11. How can I tell, with something like objdump, if an object file has been built with -fPIC?
  12. How do I run the GCC preprocessor to get the code after macros like #define are expanded?
  13. What does the compiler error “missing binary operator before token” mean?
  14. Cuda Clang and OS X Mavericks
  15. How do I set up CLion to compile and run?
  16. How can I see parse tree, intermediate code, optimization code and assembly code during COMPILATION?
  17. How to set a variable in GCC with Intel syntax inline assembly?
  18. How to retrieve the GCC version used to compile a given ELF executable?
  19. Disable specific warnings in GCC [duplicate]
  20. long double (GCC specific) and __float128
  21. Make install, but not to default directories?
  22. How to write multiline inline assembly code in GCC C++?
  23. Errors that refer to a bunch of unresolved OpenSSL symbols that clearly exist?
  24. Why do the addresses in my assembler dump differ from the addresses of registers?
  25. How does the GCC implementation of modulo (%) work, and why does it not use the div instruction?
  26. How to use AVX/pclmulqdq on Mac OS X
  27. Fast Division on GCC/ARM
  28. x86_64: Is it possible to “in-line substitute” PLT/GOT references?
  29. Tail recursion in gcc/g++
  30. Is the hash required for immediate values in ARM assembly?

Leave a Comment