You can use the function parse_printf_format to obtain
information about the number and types of arguments that are expected by
a given template string. This function permits interpreters that
provide interfaces to printf to avoid passing along invalid
arguments from the user's program, which could cause a crash.
All the symbols described in this section are declared in the header
— Function: size_t parse_printf_format (const char *template, size_t n, int *argtypes)
This function returns information about the number and types of
arguments expected by the printf template string template.
The information is stored in the array argtypes; each element of
this array describes one argument. This information is encoded using
the various `PA_' macros, listed below.
The argument n specifies the number of elements in the array
argtypes. This is the maximum number of elements that
parse_printf_format will try to write.
parse_printf_format returns the total number of arguments required
by template. If this number is greater than n, then the
information returned describes only the first n arguments. If you
want information about additional arguments, allocate a bigger
array and call parse_printf_format again.
The argument types are encoded as a combination of a basic type and
modifier flag bits.
— Macro: int PA_FLAG_MASK
This macro is a bitmask for the type modifier flag bits. You can write
the expression (argtypes[i] & PA_FLAG_MASK) to extract just the
flag bits for an argument, or (argtypes[i] & ~PA_FLAG_MASK) to
extract just the basic type code.
Here are symbolic constants that represent the basic types; they stand
for integer values.
This specifies that the base type is int.
This specifies that the base type is int, cast to char.
This specifies that the base type is char *, a null-terminated string.
This specifies that the base type is void *, an arbitrary pointer.
This specifies that the base type is float.
This specifies that the base type is double.
You can define additional base types for your own programs as offsets
from PA_LAST. For example, if you have data types `foo'
and `bar' with their own specialized printf conversions,
you could define encodings for these types as: