thought I'd collect it in one useful place. Please add and correct
any problems as you come across them.
-I'm going to start from a base of the ISO C89 standard, since that is
+I'm going to start from a base of the ISO C90 standard, since that is
probably what most people code to naturally. Obviously using
constructs introduced after that is not a good idea.
needs to be coded in some other way.
-free and realloc
-----------------
+Avoid unnecessary test before free
+----------------------------------
-Some implementations crash upon attempts to free or realloc the null
-pointer. Thus if mem might be null, you need to write
+Since SunOS 4 stopped being a reasonable portability target,
+(which happened around 2007) there has been no need to guard
+against "free (NULL)". Thus, any guard like the following
+constitutes a redundant test:
+
+ if (P)
+ free (P);
+
+It is better to avoid the test.[*]
+Instead, simply free P, regardless of whether it is NULL.
+
+[*] However, if your profiling exposes a test like this in a
+performance-critical loop, say where P is nearly always NULL, and
+the cost of calling free on a NULL pointer would be prohibitively
+high, consider using __builtin_expect, e.g., like this:
+
+ if (__builtin_expect (ptr != NULL, 0))
+ free (ptr);
- if (mem)
- free (mem);
Trigraphs
o Adding a function declaration for a module declared in another file to
a .c file instead of to a .h file.
-
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