Quest generates C code for testing C compilers. A test is run by compiling the generated code it with the compiler under test and subsequently executing the binary that the compiler produced. A compiler bug manifests itself by an assertion failure during the execution of the binary. This leads to automatic testing: generate and execute tests until an assertion failure is found.
The code generated by Quest tests one specific part of a C compiler: how it implements passing values to a function by function call and returning a value from it using the return statement. Stated simpler, the generated code by Quests checks that a value passed to a function is indeed received unaltered from the caller and likewise when a valuereturned to the caller.