RealView Compilation Tools Compiler Reference Guide - ARM ...

C and C++ Implementation Details
See the description of C language mappings in the Procedure Call Standard for the
ARM Architecture specification for more information.
Note
Care must be taken when mixing translation units that have been compiled with and
without the --enum_is_int option, and that share interfaces or data structures.
Handling values that are out of range
In strict C, enumerator values must be representable as ints, for example, they must be
in the range -2147483648 to +2147483647, inclusive. In previous releases of RVCT
out-of-range values were cast to int without a warning (unless you specified the
--strict option).
In RVCT v2.2 and above, a Warning is issued for out-of-range enumerator values:
#66: enumeration value is out of "int" range
Such values are treated the same way as in C++, that is, they are treated as unsigned int,
long long, or unsigned long long.
To ensure that out-of-range Warnings are reported, use the following command to
change them into Errors:
armcc --diag_error=66 ...
Structures
The following points apply to:
• all C structures
• all C++ structures and classes not using virtual functions or base classes.
Structure alignment
The alignment of a non-packed structure is the maximum alignment
required by any of its fields.
Field alignment
Structures are arranged with the first-named component at the lowest
address. Fields are aligned as follows:
• A field with a char type is aligned to the next available byte.
• A field with a short type is aligned to the next even-addressed byte.
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