| Message ID | 1473381053-18817-4-git-send-email-dmalcolm@redhat.com |
|---|---|
| State | New |
| Headers | show |
On Thu, Sep 08, 2016 at 08:30:47PM -0400, David Malcolm wrote: > We have a lot of global state in our code. Ideally we'd reduce the > amount of such global state, but a prerequisite for sane refactoring > is having automated testing in place to ensure that the refactoring > doesn't break anything. > > However, the global state itself makes it hard to write such automated > testing. > > To break this Catch-22, this patch introduces a class temp_override, > for temporarily assigning a value to a global variable, saving the old > value, and then restoring that old value in a dtor. I expect there are uses for this outside of selftests, so I'd suggest making it more general. I guess the name is good enough, I would have done auto_restore, but this is fine. You just need to put it somewhere generally accessible though I'm not sure what that would be. Trev
On 09/08/2016 06:30 PM, David Malcolm wrote: > We have a lot of global state in our code. Ideally we'd reduce the > amount of such global state, but a prerequisite for sane refactoring > is having automated testing in place to ensure that the refactoring > doesn't break anything. > > However, the global state itself makes it hard to write such automated > testing. > > To break this Catch-22, this patch introduces a class temp_override, > for temporarily assigning a value to a global variable, saving the old > value, and then restoring that old value in a dtor. > > gcc/ChangeLog: > * selftest.h (selftest::temp_override): New class. When you need it, this is fine. jeff
diff --git a/gcc/selftest.h b/gcc/selftest.h index e5f5c60..4c50217 100644 --- a/gcc/selftest.h +++ b/gcc/selftest.h @@ -153,6 +153,35 @@ for_each_line_table_case (void (*testcase) (const line_table_case &)); extern char *read_file (const location &loc, const char *path); +/* A fixture for temporarily overriding a global variable with a new + value. The original value of the variable is captured in the ctor, + and restored in the dtor. */ + +template <typename T> +class temp_override +{ + public: + temp_override (T& var, T new_value) + : m_var (var), + /* Record the current value of VAR. */ + m_old_value (var) + { + /* Set the var to the new value. */ + m_var = new_value; + } + + ~temp_override () + { + /* Restore the value of the variable to that stored in the + ctor. */ + m_var = m_old_value; + } + + private: + T& m_var; + T m_old_value; +}; + /* Declarations for specific families of tests (by source file), in alphabetical order. */ extern void bitmap_c_tests ();