Various kinds of errors are possible when using the API, such as mismatched types in an assignment. You can only compile and get code from a context if no errors occur.
Errors are printed on stderr and can be queried using gcc_jit_context_get_first_error().
They typically contain the name of the API entrypoint where the error occurred, and pertinent information on the problem:
./buggy-program: error: gcc_jit_block_add_assignment: mismatching types: assignment to i (type: int) from "hello world" (type: const char *)
In general, if an error occurs when using an API entrypoint, the entrypoint returns NULL. You don’t have to check everywhere for NULL results, since the API handles a NULL being passed in for any argument by issuing another error. This typically leads to a cascade of followup error messages, but is safe (albeit verbose). The first error message is usually the one to pay attention to, since it is likely to be responsible for all of the rest:
Returns the first error message that occurred on the context.
The returned string is valid for the rest of the lifetime of the context.
If no errors occurred, this will be NULL.
If you are wrapping the C API for a higher-level language that supports exception-handling, you may instead be interested in the last error that occurred on the context, so that you can embed this in an exception:
Returns the last error message that occurred on the context.
If no errors occurred, this will be NULL.
If non-NULL, the returned string is only guaranteed to be valid until the next call to libgccjit relating to this context.