50 lines
1.9 KiB
Markdown
50 lines
1.9 KiB
Markdown
# libbuild2-autoconf
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GNU Autoconf emulation build system module for `build2`.
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Specifically, this module provides an [`in`][module-in]-based rule for
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processing `config.h.in` files. Besides the Autoconf special line flavor
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(`#undef`), it also supports the CMake (`#cmakedefine`) and Meson
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(`#mesondefine`) variants.
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Similar to Autoconf, this module provides built-in support for a number of
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common `HAVE_*` configuration options. However, the values of these options
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are not discovered by dynamic probing, such as trying to compile a test
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program to check if the feature is present. Instead, they are set to static
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expected values based on the platform/compiler macros (see note at the
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beginning of [Project Configuration][proj-config] for rationale).
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See [`libbuild2/autoconf/checks/`][checks] for the list of available build-in
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configuration options.
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## Adding new configuration options.
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To add a new configuration option `<NAME>` simply create the `<NAME>.h` header
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file with the corresponding check and place it into
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[`libbuild2/autoconf/checks/`][checks] (use existing checks for inspiration).
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The first line in this header file must be in the form:
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```
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// <NAME>
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```
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Subsequent lines should be C-style comments or preprocessor directives that
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`#define` or `#undef` `<NAME>` depending on whether the feature is available
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(though there can be idiosyncrasies; see `const.h`, for example). Note that
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there should be no double-quotes or backslashes except for line
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continuations. For example:
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```
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// HAVE_FOO
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#ifndef _WIN32
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# define HAVE_FOO 1
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#else
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# undef HAVE_FOO /* No foo on Windows. */
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#endif
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```
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[module-in]: https://build2.org/build2/doc/build2-build-system-manual.xhtml#module-in
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[proj-config]: https://build2.org/build2/doc/build2-build-system-manual.xhtml#proj-config
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[checks]: https://github.com/build2/libbuild2-autoconf/tree/master/libbuild2-autoconf/libbuild2/autoconf/checks/
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