Search code examples
llvmllvm-ir

How to share cl::opt arguments between passes?

I have defined a cl::opt parameter in one of my pass.

cl::opt<std::string> input("input", cl::init(""), cl::desc("the input file"), cl::value_desc("the input file"));

I wonder that how to share this parameter with another pass? I have tried to move it to a header file and let the another pass include it, but it reported a multiple definition error.

Solution

  • You need to make an option's storage external.

    In some shared header file declare a variable:

    extern std::string input;

    And define it and the command line option itself in only one of your sources:

    std::string input;
static cl::opt<std::string, true> inputFlag("input", cl::init(""), cl::desc("the input file"), cl::value_desc("the input file"), cl::location(input));

    Note added cl::location(input) argument, which instructs cl::opt to store the command line option's value in the input variable. Now you can access inputs value from different TUs, but still have only one definition.

    Note that the variable that captures the command line option (inputFlag) is a global variable in the TU in which it is defined in. It is a good idea to give it internal linkage via the static keyword.

    See Internal and External storage section.