cdl_option <name> {
- define [-file=<filename>] [-format=<format>] <symbol>
- …
-} |
Normally the configuration system generates a single -#define for each option that is active and enabled, -with the defined symbol being the name of the option. These -#define's go to the package's own configuration -header file, for example pkgconf/kernel.h -for kernel configuration options. For the majority of options this is -sufficient. Sometimes it is useful to have more control over which -#define's get generated.
The define property can be used to generate an addition -#define if the option is both active and enabled, -for example:
cdl_option CYGNUM_LIBC_STDIO_FOPEN_MAX {
- …
- define FOPEN_MAX
-} |
If this option is given the value 40 then the following -#define's will be generated in the configuration -header pkgconf/libc.h:
#define CYGNUM_LIBC_STDIO_FOPEN_MAX 40 -#define FOPEN_MAX 40 |
The default #define can be suppressed if desired -using the no_define property. This is useful if the symbol should -only be defined in -pkgconf/system.h and not in -the package's own configuration header file. The value that will be -used for this #define is the same as for the -default one, and depends on the option's flavor as follows:
Options with this flavor are always enabled and have no value, so the -constant 1 will be used.
If the option is disabled then no #define will be -generated. Otherwise the constant 1 will be used.
If the option is disabled then no #define will be -generated. Otherwise the option's current value will be used.
The option's current value will be used.
For active options with the data flavor, and for -active and enabled options with the booldata -flavor, either one or two #define's will be -generated. These take the following forms:
#define <symbol> <value> -#define <symbol>_<value> |
For the first #define it is possible to control the -format used for the value using a --format=<format> option. For example, the -following can be used to output some configuration data as a C string:
cdl_option <name> {
- …
- define -format="\\\"%s\\\"" <symbol>
-} |
The implementation of this facility involves concatenating the -Tcl command format, the format string, and the -string representation of the option's value, and evaluating this in a -Tcl interpreter. Therefore the format string will be processed twice -by a Tcl parser, and appropriate care has to be taken with quoting.
The second #define will be generated only if is a -valid C preprocessor macro symbol. By default the symbols generated by -define properties will end up in the package's own configuration -header file. The -file option can be used to -specify an alternative destination. At the time of writing the only -valid alternative definition is -file=system.h, -which will send the output to the global configuration header file -pkgconf/system.h.
| Caution |
Care has to be taken with the -format option. -Because the Tcl interpreter's format command is -used, this property is subject to any problems with the implementation -of this in the Tcl library. Generally there should be no problems with -string data or with integers up to 32 bits, but there may well be -problems if 64-bit data is involved. This issue may be addressed in a -future release. |