Wrapping C Constants

When SWIG encounters C preprocessor macros and C declarations that look like constants, it creates a Go constant with an identical value. Click here to see a SWIG interface with some constant declarations in it.

Accessing Constants from Go

Click here to see a Go program that prints out the values of the constants contained in the above file.

Key points

• All names are capitalized to make them visible.
• The values of preprocessor macros are converted into Go constants.
• C string literals such as "Hello World" are converted into Go strings.
• Macros that are not fully defined are simply ignored. For example:

  #define EXTERN extern
  

  is ignored because SWIG has no idea what type of variable this would be.

• Expressions are allowed provided that all of their components are defined. Otherwise, the constant is ignored.
• Certain C declarations involving 'const' are also turned into Go constants.
• The constants that appear in a SWIG interface file do not have to appear in any sort of matching C source file since the creation of a constant does not require linkage to a stored value (i.e., a value held in a C global variable or memory location).