Add test script to generate a static library with a custom target.

docs/markdown/Reference-manual.md

@@ -334,6 +334,7 @@ the following special string substitutions:
 - `@DEPFILE@` the full path to the dependency file passed to `depfile`
 - `@PLAINNAME@`: the input filename, without a path
 - `@BASENAME@`: the input filename, with extension removed
+- `@PRIVATE_DIR@`: path to a directory where the custom target must store all its intermediate files, available since 0.50.1
 
 The `depfile` keyword argument also accepts the `@BASENAME@` and `@PLAINNAME@`
 substitutions. *(since 0.47)*

mesonbuild/backend/backends.py

@@ -964,6 +964,12 @@ class Backend:
                     raise MesonException(msg)
                 dfilename = os.path.join(outdir, target.depfile)
                 i = i.replace('@DEPFILE@', dfilename)
+            elif '@PRIVATE_DIR@' in i:
+                if target.absolute_paths:
+                    pdir = self.get_target_private_dir_abs(target)
+                else:
+                    pdir = self.get_target_private_dir(target)
+                i = i.replace('@PRIVATE_DIR@', pdir)
             elif '@PRIVATE_OUTDIR_' in i:
                 match = re.search(r'@PRIVATE_OUTDIR_(ABS_)?([^/\s*]*)@', i)
                 if not match:

test cases/common/216 link custom/custom_stlib.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+
+import os, sys, subprocess, argparse, pathlib
+
+parser = argparse.ArgumentParser()
+
+parser.add_argument('--private-dir', required=True)
+parser.add_argument('-o', required=True)
+parser.add_argument('cmparr', nargs='+')
+
+static_linker = 'ar'
+
+contents = '''#include<stdio.h>
+
+void flob() {
+    printf("Now flobbing.\\n");
+}
+'''
+
+def generate_lib(outfile, private_dir, compiler_array):
+    outdir = pathlib.Path(private_dir)
+    if not outdir.exists():
+        outdir.mkdir()
+    c_file = outdir / 'flob.c'
+    c_file.write_text(contents)
+    o_file = c_file.with_suffix('.o')
+    compile_cmd = compiler_array + ['-c', '-g', '-O2', '-o', o_file, c_file]
+    subprocess.check_call(compile_cmd)
+    out_file = pathlib.Path(outfile)
+    if out_file.exists():
+        out_file.unlink()
+    link_cmd = [static_linker, 'csrD', outfile, o_file]
+    subprocess.check_call(link_cmd)
+
+if __name__ == '__main__':
+    options = parser.parse_args()
+    generate_lib(options.o, options.private_dir, options.cmparr)
+    sys.exit(1)

test cases/common/216 link custom/meson.build

@@ -0,0 +1,20 @@
+project('linkcustom', 'c')
+
+# This would require passing the static linker to the build script or having
+# it detect it by itself. I'm too lazy to implement it now and it is not
+# really needed for testing that custom targets work. It is the responsibility
+# of the custom target to produce things in the correct format.
+assert(not meson.is_cross(), 'MESON_SKIP_TEST cross checking not implemented.')
+
+cc = meson.get_compiler('c')
+genprog = find_program('custom_stlib.py')
+
+clib = custom_target('linkcustom',
+  output: 'libflob.a',
+  command: [genprog,
+            '-o', '@OUTPUT@',
+            '--private-dir', '@PRIVATE_DIR@'] + cc.cmd_array())
+
+#exe = executable('prog', 'prog.c', link_with: clib)
+#test('linkcustom', exe)
+