How can I Access Compiler-Instantiated Template Implementations in C with Clang?

Accessing Compiler-Instantiated Template Implementations

In C , function and class templates allow for code generation at compile time based on user-specified parameters. This process of code instantiation can be valuable for understanding the optimizations performed by the compiler. However, the default compiler output does not typically include these instantiated implementations.

Clang AST Pretty-Printing

Clang, a popular C compiler, offers a mechanism for visualizing compiler-instantiated template code. Using the -Xclang -ast-print flag with the -fsyntax-only option, one can extract the Abstract Syntax Tree (AST) of the instantiated template.

Example Usage

Consider the following code snippet:

<code class="cpp">template <class T> T add(T a, T b) {
    return a + b;
}</code>

To view the instantiated implementation for the int template specialization, we can use the following command:

$ clang++ -Xclang -ast-print -fsyntax-only test.cpp

Output:

The output will include the compiler-generated implementation for the add function template, specialized for the int type:

template <class T> T add(T a, T b) {
    return a + b;
}
template<> int add<int>(int a, int b) {
    return a + b;
}

Additional Notes

• This technique is particularly useful for debugging template code and understanding compiler optimizations.
• The output format may vary depending on the specific version of Clang used.

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