gettext: gfc-internal-format
15.3.26 GFC internal Format Strings
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These format strings are used inside the GNU Fortran Compiler
sources, that is, the Fortran frontend in the GCC sources. In such a
format string, a directive starts with ‘%’ and is finished by a
specifier: ‘%’ denotes a literal percent sign, ‘C’ denotes the current
source location, ‘L’ denotes a source location, ‘c’ denotes a character,
‘s’ denotes a string, ‘i’ and ‘d’ denote an integer, ‘u’ denotes an
unsigned integer. ‘i’, ‘d’, and ‘u’ may be preceded by a size specifier
‘l’.