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C preprocessor: Difference between revisions
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The C preprocessor is a powerful tool and properly used may be very useful.
The following have been checked to work in GCC.
=== Uses for debugging ===▼
=== Hazards of the C preprocessor ===▼
=== Rules ===
=== Uses ===
▲==== Uses for debugging ====
==== Deleted Code ====
A code block may be commented out to delete it from the program, however nesting deleted fragments may reduce legibility with C++ style comments, and C comments do not nest at all.
A better solution is to wrap the code in and #if 0-#endif block, where the conditional 0 means false :
[code]
#if 0
print("memory state: ");
print(mem->state);
print("\nallocated blocks: ");
print(mem->allocs);
#endif
[/code]
Many editors, like [[VIm]] have by default syntax highlighting rules that treat such #if 0-#endif blocks as comments.
The #if-#endif directives must be balanced, single-quotes characters must balance etc. so for deleting non-code text use comments instead.
▲=== Hazards of the C preprocessor ===
There is a number of counter-intuitive consequences of macros and macro expanding design.
[http://gcc.gnu.org/onlinedocs/cpp/Macro-Pitfalls.html#Macro-Pitfalls Macro Pitfalls]
== See also ==
* [[C]]
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