Category
Pragma equivalent
#pragma options [no]macpstr
Purpose
Converts Pascal string literals (prefixed by the \p escape sequence) into null-terminated strings in which the first byte contains the length of the string.
“\pABC”'\03' , 'A' , 'B' , 'C' , '\0'
Defaults
-qnomacpstr
Usage
A Pascal string literal always contains the characters "\p. The characters \p in the middle of a string do not form a Pascal string literal, and must be immediately preceded by the " (double quote) character.
'\p' , 'A' , 'B' , 'C' , '\0'The compiler ignores the -qmacpstr option when the -qmbcs or -qdbcs option is active because Pascal-string-literal processing is only valid for one-byte characters.
The #pragma options keyword macpstr is only valid at the top of a source file before any C source statements. If you attempt to use it in the middle of a source file, it is ignored and the compiler issues an error message.
The following describes how Pascal string literals are processed.
- Because there is no Pascal-string-literal processing of wide strings, using the escape sequence \p in a wide string literal with the -qmacpstr option, generates a warning message and the escape sequence is ignored.
- Concatenating a Pascal string literal to a normal string gives
a non-Pascal string. For example, concatenating the strings:
gives:“ABC” “\pDEF”“ABCpDEF” - Concatenating two Pascal string literals, for example, strcat,
does not result in a Pascal string literal. However, as described
above, two adjacent Pascal string literals can be concatenated to
form one Pascal string literal in which the first byte is the length
of the new string literal. For example, concatenating the strings:
“\p ABC” “\p DEF”or
results in:“\p ABC” “DEF”“\06ABCDEF” - A Pascal string literal cannot be concatenated with a wide string literal.
- The compiler truncates a Pascal string literal that is longer than 255 bytes (excluding the length byte and the terminating NULL) to 255 characters.
- The Pascal string literal is not a basic type different from other C string literals. After the processing of the Pascal string literal is complete, the resulting string is treated the same as all other strings. If the program passes a C string to a function that expects a Pascal string, or vice versa, the behavior is undefined.
- Modifying any byte of the Pascal string literal after the processing has been completed does not alter the original length value in the first byte. For example, in the string “\06ABCDEF”, substituting a null character for one of the existing characters in the middle of the string does not change the value of the first byte of the string, which contains the length of the string.
- No errors or warnings are issued when the bytes of the processed Pascal string literal are modified.
Predefined macros
None.
Examples
xlc mypascal.c -qmacpstr