The following points apply to the character sets and identifiers expected by the compiler:
Uppercase and lowercase characters are distinct in all internal and external identifiers. An identifier can also contain a dollar
($)character unless the
--strictcompiler option is specified. To permit dollar signs in identifiers with the
--strictoption, also use the
setlocale(LC_CTYPE, "ISO8859-1")makes the
islower()functions behave as expected over the full 8-bit Latin-1 alphabet, rather than over the 7-bit ASCII subset. The locale must be selected at link time.
Source files are compiled according to the currently selected locale. You might have to select a different locale, with the
--localecommand-line option, if the source file contains non-ASCII characters. See Compiler command-line options listed by group in Using the Compiler for more information.
The compiler supports multibyte character sets, such as Unicode.
Other properties of the source character set are host-specific.
The properties of the execution character set are target-specific. The ARM C and C++ libraries support the ISO 8859-1 (Latin-1 Alphabet) character set with the following consequences:
The execution character set is identical to the source character set.
There are eight bits in a character in the execution character set.
There are four characters (bytes) in an int. If the memory system is:
The bytes are ordered from least significant at the lowest address to most significant at the highest address.
The bytes are ordered from least significant at the highest address to most significant at the lowest address.
In C all character constants have type int. In C++ a character constant containing one character has the type char and a character constant containing more than one character has the type int. Up to four characters of the constant are represented in the integer value. The last character in the constant occupies the lowest-order byte of the integer value. Up to three preceding characters are placed at higher-order bytes. Unused bytes are filled with the
Table 31 lists all integer character constants, that contain a single character or character escape sequence, are represented in both the source and execution character sets.
Table 31. Character escape codes Escape sequence Char value Description
New line (line feed)
ASCII code in hexadecimal
ASCII code in octal
Characters of the source character set in string literals and character constants map identically into the execution character set.
Data items of type char are unsigned by default. They can be explicitly declared as signed char or unsigned char:
--signed_charsoption can be used to make the char signed
--unsigned_charsoption can be used to make the char unsigned.
Care must be taken when mixing translation units that have been compiled with and without the
--unsigned_charsoptions, and that share interfaces or data structures.
The ARM ABI defines char as an unsigned byte, and this is the interpretation used by the C++ libraries supplied with the ARM compilation tools.
No locale is used to convert multibyte characters into the corresponding wide characters for a wide character constant. This is not relevant to the generic implementation.