build: Add a separate configuration step

1 files changed, 44 insertions, 39 deletions

diff --git a/docs/BUILDING.md b/docs/BUILDING.md
index 7eb3a37..abf6185 100644
--- a/docs/BUILDING.md
+++ b/docs/BUILDING.md
@@ -7,9 +7,10 @@ Compiling
 `bfs` uses [GNU Make](https://www.gnu.org/software/make/) as its build system.
 A simple invocation of
 
+    $ make config
     $ make
 
-should build `bfs` successfully, with no additional steps necessary.
+should build `bfs` successfully.
 As usual with `make`, you can run a [parallel build](https://www.gnu.org/software/make/manual/html_node/Parallel.html) with `-j`.
 For example, to use all your cores, run `make -j$(nproc)`.
 
@@ -17,25 +18,28 @@ For example, to use all your cores, run `make -j$(nproc)`.
 
 | Command          | Description                                                   |
 |------------------|---------------------------------------------------------------|
+| `make config`    | Configures the build system                                   |
 | `make`           | Builds just the `bfs` binary                                  |
 | `make all`       | Builds everything, including the tests (but doesn't run them) |
 | `make check`     | Builds everything, and runs the tests                         |
 | `make install`   | Installs `bfs` (with man page, shell completions, etc.)       |
 | `make uninstall` | Uninstalls `bfs`                                              |
+| `make clean`     | Delete the build products                                     |
+| `make mrclean`   | Delete all generated files, including the build configuration |
 
-### Flag-like targets
+### Build profiles
 
-The build system provides a few shorthand targets for handy configurations:
+The configuration system provides a few shorthand flags for handy configurations:
 
-| Command        | Description                                                 |
-|----------------|-------------------------------------------------------------|
-| `make release` | Build `bfs` with optimizations, LTO, and without assertions |
-| `make asan`    | Enable [AddressSanitizer]                                   |
-| `make lsan`    | Enable [LeakSanitizer]                                      |
-| `make msan`    | Enable [MemorySanitizer]                                    |
-| `make tsan`    | Enable [ThreadSanitizer]                                    |
-| `make ubsan`   | Enable [UndefinedBehaviorSanitizer]                         |
-| `make gcov`    | Enable [code coverage]                                      |
+| Command                 | Description                                                 |
+|-------------------------|-------------------------------------------------------------|
+| `make config RELEASE=y` | Build `bfs` with optimizations, LTO, and without assertions |
+| `make config ASAN=y`    | Enable [AddressSanitizer]                                   |
+| `make config LSAN=y`    | Enable [LeakSanitizer]                                      |
+| `make config MSAN=y`    | Enable [MemorySanitizer]                                    |
+| `make config TSAN=y`    | Enable [ThreadSanitizer]                                    |
+| `make config UBSAN=y`   | Enable [UndefinedBehaviorSanitizer]                         |
+| `make config GCOV=y`    | Enable [code coverage]                                      |
 
 [AddressSanitizer]: https://github.com/google/sanitizers/wiki/AddressSanitizer
 [LeakSanitizer]: https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer#stand-alone-mode
@@ -44,38 +48,38 @@ The build system provides a few shorthand targets for handy configurations:
 [UndefinedBehaviorSanitizer]: https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html
 [code coverage]: https://gcc.gnu.org/onlinedocs/gcc/Gcov.html
 
-You can combine multiple flags and other targets (e.g. `make asan ubsan check`), but not all of them will work together.
+You can combine multiple profiles (e.g. `make config ASAN=y UBSAN=y`), but not all of them will work together.
 
 ### Flags
 
-Other flags are controlled with `make` variables and/or environment variables.
-Here are some of the common ones; check the [`GNUmakefile`](/GNUmakefile) for more.
-
-| Flag                             | Description                                 |
-|----------------------------------|---------------------------------------------|
-| `CC`                             | The C compiler to use, e.g. `make CC=clang` |
-| `CFLAGS`<br>`EXTRA_CFLAGS`       | Override/add to the default compiler flags  |
-| `LDFLAGS`<br>`EXTRA_LDFLAGS`     | Override/add to the linker flags            |
-| `USE_ACL`<br>`USE_LIBCAP`<br>... | Enable/disable [optional dependencies]      |
-| `TEST_FLAGS`                     | `tests.sh` flags for `make check`           |
-| `BUILDDIR`                       | The build output directory (default: `.`)   |
-| `DESTDIR`                        | The root directory for `make install`       |
-| `PREFIX`                         | The installation prefix (default: `/usr`)   |
-| `MANDIR`                         | The man page installation directory         |
+Other flags can be specified on the `make config` command line or in the environment.
+Here are some of the common ones; check the [`Makefile`](/Makefile) for more.
+
+| Flag                             | Description                                        |
+|----------------------------------|----------------------------------------------------|
+| `CC`                             | The C compiler to use, e.g. `make config CC=clang` |
+| `CFLAGS`<br>`EXTRA_CFLAGS`       | Override/add to the default compiler flags         |
+| `LDFLAGS`<br>`EXTRA_LDFLAGS`     | Override/add to the linker flags                   |
+| `USE_ACL`<br>`USE_LIBCAP`<br>... | Enable/disable [optional dependencies]             |
+| `TEST_FLAGS`                     | `tests.sh` flags for `make check`                  |
+| `BUILDDIR`                       | The build output directory (default: `.`)          |
+| `DESTDIR`                        | The root directory for `make install`              |
+| `PREFIX`                         | The installation prefix (default: `/usr`)          |
+| `MANDIR`                         | The man page installation directory                |
 
 [optional dependencies]: #dependencies
 
 ### Dependencies
 
 `bfs` depends on some system libraries for some of its features.
-These dependencies are optional, and can be turned off at build time if necessary by setting the appropriate variable to the empty string (e.g. `make USE_ONIGURUMA=`).
+These dependencies are optional, and can be turned off in `make config` if necessary by setting the appropriate variable to `n` (e.g. `make config USE_ONIGURUMA=n`).
 
-| Dependency  | Platforms  | `make` flag     |
-|-------------|------------|-----------------|
-| [acl]       | Linux only | `USE_ACL`       |
-| [libcap]    | Linux only | `USE_LIBCAP`    |
-| [liburing]  | Linux only | `USE_LIBURING`  |
-| [Oniguruma] | All        | `USE_ONIGURUMA` |
+| Dependency  | Platforms  | `make config` flag |
+|-------------|------------|--------------------|
+| [acl]       | Linux only | `USE_ACL`          |
+| [libcap]    | Linux only | `USE_LIBCAP`       |
+| [liburing]  | Linux only | `USE_LIBURING`     |
+| [Oniguruma] | All        | `USE_ONIGURUMA`    |
 
 [acl]: https://savannah.nongnu.org/projects/acl
 [libcap]: https://sites.google.com/site/fullycapable/
@@ -84,21 +88,22 @@ These dependencies are optional, and can be turned off at build time if necessar
 
 ### Dependency tracking
 
-The build system automatically tracks header dependencies with the `-M` family of compiler options (see `DEPFLAGS` in the [`GNUmakefile`](/GNUmakefile)).
+The build system automatically tracks header dependencies with the `-M` family of compiler options (see `DEPFLAGS` in the [`Makefile`](/Makefile)).
 So if you edit a header file, `make` will rebuild the necessary object files ensuring they don't go out of sync.
 
+We also add a dependency on the current configuration, so you can change configurations and rebuild without having to `make clean`.
+
 We go one step further than most build systems by tracking the flags that were used for the previous compilation.
 That means you can change configurations without having to `make clean`.
 For example,
 
+    $ make config
+    $ make
+    $ make config RELEASE=y
     $ make
-    $ make release
 
 will build the project in debug mode and then rebuild it in release mode.
 
-A side effect of this may be surprising: `make check` by itself will rebuild the project in the default configuration.
-To test a different configuration, you'll have to repeat it (e.g. `make release check`).
-
 
 Testing
 -------