Does the C preprocessor strip comments or expand macros first? [duplicate]

by

Unfortunately, the original ANSI C Specification specifically excludes any Preprocessor features in section 4 (“This specification describes only the C language. It makes no provision for either the library or the preprocessor.”).

The C99 specification handles this explicity, though. The comments are replaced with a single space in the “translation phase”, which happens prior to the Preprocessing directive parsing. (Section 6.10 for details).

VC++ and the GNU C Compiler both follow this paradigm – other compilers may not be compliant if they’re older, but if it’s C99 compliant, you should be safe.

Related Contents:

  1. Standard alternative to GCC’s ##__VA_ARGS__ trick?
  2. How does the below program output `C89` when compiled in C89 mode and `C99` when compiled in C99 mode?
  3. Is it possible to iterate over arguments in variadic macros?
  4. Why does the C preprocessor interpret the word “linux” as the constant “1”?
  5. MIN and MAX in C
  6. #pragma pack effect
  7. What is the behavior of integer division?
  8. #define macro for debug printing in C?
  9. Overloading Macro on Number of Arguments
  10. How to make a variadic macro (variable number of arguments)
  11. Catch Ctrl-C in C
  12. How can I concatenate twice with the C preprocessor and expand a macro as in “arg ## _ ## MACRO”?
  13. “#include” a text file in a C program as a char[]
  14. What does dot (.) mean in a struct initializer?
  15. What is the difference between C, C99, ANSI C and GNU C?
  16. What is the fastest/most efficient way to find the highest set bit (msb) in an integer in C?
  17. Printf width specifier to maintain precision of floating-point value
  18. Are typedef and #define the same in c?
  19. Can gcc output C code after preprocessing?
  20. Can’t understand this way to calculate the square of a number
  21. Indenting #defines
  22. What predefined macro can I use to detect clang?
  23. Macro definition to determine big endian or little endian machine?
  24. How to compare strings in C conditional preprocessor-directives
  25. Is “inline” without “static” or “extern” ever useful in C99?
  26. Concatenate int to string using C Preprocessor
  27. Are there machines, where sizeof(char) != 1, or at least CHAR_BIT > 8?
  28. Why do most C developers use define instead of const? [duplicate]
  29. Understanding container_of macro in the Linux kernel
  30. Finding out what the GCC include path is [duplicate]
  31. #ifdef inside #define
  32. Easy way to use variables of enum types as string in C?
  33. C99 boolean data type?
  34. Why only define a macro if it’s not already defined?
  35. Printing null pointers with %p is undefined behavior?
  36. What are the applications of the ## preprocessor operator and gotchas to consider?
  37. This obfuscated C code claims to run without a main(), but what does it really do?
  38. Real-world use of X-Macros
  39. What are C macros useful for?
  40. Understanding the behavior of C’s preprocessor when a macro indirectly expands itself
  41. state machines tutorials [closed]
  42. Preprocessor check if multiple defines are not defined
  43. What are the most useful new features in C99? [closed]
  44. Should I use #include in headers?
  45. What is the default C -std standard version for the current GCC (especially on Ubuntu)?
  46. What is the use of the `inline` keyword in C?
  47. Why not concatenate C source files before compilation? [duplicate]
  48. How to write a while loop with the C preprocessor?
  49. Array-size macro that rejects pointers
  50. Seeing expanded C macros

Leave a Comment