C251 User's Guide

PACK Compiler Directive

Abbreviation	None.
Arguments	A decimal number (1 or 2) enclosed in parentheses.
Default	PACK(2)
µVision	Options — C251 — Misc Controls.
Description	The PACK directive causes the compiler to generate byte-aligned or half-word-aligned structures. This is useful when exchanging data with other systems where no alignment is required. Note By default, the compiler assumes that structure members are aligned on byte boundaries. PACK(2) may increase the size of a structure since alignment gaps are inserted for padding.
Example	#pragma pack(1) /* byte alignment / struct s1 { int i1; // i1 has offset 0 char c1; // c1 has offset 2 int i2; // i2 has offset 3 char c2; // c2 has offset 5 int i3; // i3 has offset 6 char z1; // z1 has offset 8 }; #pragma pack() / reset to default alignment */ struct s2 { int i1; // i1 has offset 0 char c1; // c1 has offset 2 int i2; // i2 has offset 4 char c2; // c2 has offset 6 int i3; // i3 has offset 8 char z1; // z1 has offset 10 };