Texas Instruments TMS320C2x, User Manual

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Compatibility with K&R C
5-15 TMS320C2x/C2xx/C5x C Language
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ANSI interprets file scope definitions that have no initializers as tentative
definitions . In a single module, multiple definitions of this form are fused
together into a single definition. Under K&R, each definition is treated as
a separate definition, resulting in multiple definitions of the same object
(and usually an error). For example:
int a;
int a;
/* illegal if −pk used, OK if not */
Under ANSI, the result of these two declarations is a single definition for
the object a. For most K&R compilers, this sequence is illegal, because a
is defined twice.
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ANSI prohibits, but K&R allows, objects with external linkage to be
redeclared as static:
extern int a;
static int a;
/* illegal unless −pk used */
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Unrecognized escape sequences in string and character constants are
explicitly illegal under ANSI but ignored under K&R:
char c = ’\q’; /* same as ’q’ if −pk, error if not */
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ANSI specifies that bit fields must be of type integer or unsigned. With
− pk, bit fields can be legally defined with any integral type. For example:
struct s
{
short f : 2; /* illegal unless −pk used */
};
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K&R syntax allows a trailing comma in enumerator lists:
enum { a, b, c, }; /* illegal unless −pk used */
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K&R syntax allows trailing tokens on preprocessor directives:
#endif NAME /* illegal unless −pk used */