Add support for dynamic dependencies in ad hoc Buildscript recipes

Specifically, add the new `depdb dyndep` builtin that can be used to extract
dynamic dependencies from a program run or a file. For example:

obje{hello.o}: cxx{hello}
{{
  s = $path($<[0])

  depdb dyndep $cxx.poptions $cc.poptions --what=header --default-prereq-type=h -- $cxx.path $cxx.poptions $cc.poptions $cxx.mode -M -MG $s

  diag c++ ($<[0])

  o = $path($>)
  $cxx.path $cxx.poptions $cc.poptions $cc.coptions $cxx.coptions $cxx.mode -o $o -c $s
}}

Currently only the `make` dependency format is supported.

1 files changed, 90 insertions, 0 deletions

diff --git a/libbuild2/make-parser.test.cxx b/libbuild2/make-parser.test.cxx
new file mode 100644
index 0000000..189407a
--- /dev/null
+++ b/libbuild2/make-parser.test.cxx
@@ -0,0 +1,90 @@
+// file      : libbuild2/make-parser.test.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <iostream>
+
+#include <libbuild2/types.hxx>
+#include <libbuild2/utility.hxx>
+
+#include <libbuild2/make-parser.hxx>
+#include <libbuild2/diagnostics.hxx>
+
+#undef NDEBUG
+#include <cassert>
+
+using namespace std;
+
+namespace build2
+{
+  int
+  main (int, char* argv[])
+  {
+    bool strict (false);
+
+    // Fake build system driver, default verbosity.
+    //
+    init_diag (1);
+    init (nullptr, argv[0]);
+
+    path_name in ("<stdin>");
+
+    try
+    {
+      cin.exceptions (istream::badbit);
+
+      using make_state = make_parser;
+      using make_type = make_parser::type;
+
+      make_parser make;
+
+      location ll (in, 1);
+      for (string l; !eof (getline (cin, l)); ++ll.line)
+      {
+        if (make.state == make_state::end)
+        {
+          cout << endl;
+          make.state = make_state::begin;
+        }
+
+        // Skip leading blank lines to reduce output noise.
+        //
+        if (make.state == make_state::begin && l.empty ())
+          continue;
+
+        size_t pos (0);
+        do
+        {
+          pair<make_type, string> r (make.next (l, pos, ll, strict));
+
+          cout << (r.first == make_type::target ? 'T' : 'P');
+
+          if (!r.second.empty ())
+            cout << ' ' << r.second;
+
+          cout << endl;
+        }
+        while (pos != l.size ());
+      }
+
+      if (make.state != make_state::end && make.state != make_state::begin)
+        fail (ll) << "incomplete make dependency declaration";
+    }
+    catch (const io_error& e)
+    {
+      cerr << "unable to read stdin: " << e << endl;
+      return 1;
+    }
+    catch (const failed&)
+    {
+      return 1;
+    }
+
+    return 0;
+  }
+}
+
+int
+main (int argc, char* argv[])
+{
+  return build2::main (argc, argv);
+}