# Vault 7: Projects

This publication series is about specific projects related to the Vault 7 main publication.

### Protego

# MPLAB XC16 C-Compiler

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MPLAB
®
XC16 C Compiler Users Guide
DS50002071C-page 40  2012-2013 Microchip Technology Inc.
2.5.11 Packing Objects
The __pack specifier may be used to indicate that structures should not use memory
gaps to align structure members, or that individual structure members should not be
aligned.
Use the native keywords discussed in the Differences section to look up information on
the semantics of this specifier.
Some compilers may not pad structures with alignment gaps for some devices and use
of this specifier for such devices will be ignored.
2.5.11.1 EXAMPLE
The following shows a structure qualified using __pack as well as a structure where
one member has been explicitly packed.
__pack struct DATAPOINT {
unsigned char type;
int value;
} x-point;
struct LINETYPE {
unsigned char type;
__pack int start;
long total;
} line;
2.5.11.2 DIFFERENCES
The __pack specifier is a new CCI specifier available with XC8. This specifier has no
apparent effect since the device memory is byte addressable for all data objects.
The 16- and 32-bit compilers have used the packed attribute to indicate that a struc-
ture member was not aligned with a memory gap.
2.5.11.3 MIGRATION TO THE CCI
No migration is required for XC8.
For 16- and 32-bit compilers, change any occurrence of the packed attribute, as in the
following example:
struct DOT
{
char a;
int x[2] __attribute__ ((packed));
};
to:
struct DOT
{
char a;
__pack int x[2];
};
Alternatively, you may pack the entire structure, if required.
2.5.11.4 CAVEATS
None.

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