I have an old macro that doesn't seem to work any more....
I have an old macro
#define CTRL(c) ('c' & 037)
that doesn't seem to work any more.
The intended use of this macro is in code like
tchars.t_eofc = CTRL(D);
which is expected to expand to
tchars.t_eofc = ('D' & 037); based on the assumption that the actual value of the parameter c will be substituted even inside the single quotes of a character constant. Preprocessing was never supposed to work this way; it was somewhat of an accident that a CTRL() macro like this ever worked.
ANSI C defines a new ``stringizing'' operator , but there is no corresponding ``charizing'' operator.
The best solution to the problem is probably to move the single quotes from the definition to the invocation, by rewriting the macro as
#define CTRL(c) ((c) & 037)
and invoking it as
(Doing so also makes the macro ``syntactic'';
It may also be possible to use the stringizing operator and some indirection:
#define CTRL(c) (*#c & 037)
#define CTRL(c) (#c & 037)
but neither of these would work as well as the original, since they wouldn't be valid in case labels or as global variable initializers. (Global variable initializers and case labels require various flavors of constant expressions, and string literals and indirection aren't allowed.)
2016-01-25, 1043👍, 0💬
How To Enter Boolean Values in SQL Statements? - MySQL FAQs - Introduction to SQL Basics If you want...
Where are cookies actually stored on the hard disk? This depends on the user's browser and OS. In th...
What does AddressOf operator do in background ? The AddressOf operator creates a delegate object to ...
How do I use forms? The basic syntax for a form is: <FORM ACTION="[URL]">...&l t;/FORM>Wh...
Rachel opened her math book and found that the sum of the facing pages was 245. What pages did she o...