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// file : build/algorithm.cxx -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Tools CC
// license : MIT; see accompanying LICENSE file
#include <build/algorithm>
#include <memory> // unique_ptr
#include <utility> // move
#include <cassert>
#include <build/path>
#include <build/scope>
#include <build/target>
#include <build/prerequisite>
#include <build/rule>
#include <build/search>
#include <build/utility>
#include <build/diagnostics>
using namespace std;
namespace build
{
target&
search (prerequisite& p)
{
assert (p.target == nullptr);
if (target* t = p.type.search (p))
return *t;
return create_new_target (p);
}
void
match_impl (action a, target& t)
{
for (auto tt (&t.type ());
tt != nullptr && !t.recipe (a);
tt = tt->base)
{
auto i (current_rules->find (tt->id));
if (i == current_rules->end () || i->second.empty ())
continue; // No rules registered for this target type, try base.
const auto& rules (i->second); // Hint map.
// @@ TODO
//
// Different rules can be used for different operations (update
// vs test is a good example). So, at some point, we will probably
// have to support a list of hints or even an operation-hint map
// (e.g., 'hint=cxx test=foo' if cxx supports the test operation
// but we want the foo rule instead). This is also the place where
// the '{build clean}=cxx' construct (which we currently do not
// support) can come handy.
//
// Also, ignore the hint (that is most likely ment for a different
// operation) if this is a unique match.
//
string hint;
auto rs (rules.size () == 1
? make_pair (rules.begin (), rules.end ())
: rules.find_prefix (hint));
for (auto i (rs.first); i != rs.second; ++i)
{
const string& n (i->first);
const rule& ru (i->second);
void* m (nullptr);
{
auto g (
make_exception_guard (
[](target& t, const string& n)
{
info << "while matching rule " << n << " for target " << t;
},
t, n));
m = ru.match (a, t, hint);
}
if (m != nullptr)
{
// Do the ambiguity test.
//
bool ambig (false);
diag_record dr;
for (++i; i != rs.second; ++i)
{
const string& n1 (i->first);
const rule& ru1 (i->second);
void* m1;
{
auto g (
make_exception_guard (
[](target& t, const string& n1)
{
info << "while matching rule " << n1 << " for target "
<< t;
},
t, n1));
m1 = ru1.match (a, t, hint);
}
if (m1 != nullptr)
{
if (!ambig)
{
dr << fail << "multiple rules matching target " << t
<< info << "rule " << n << " matches";
ambig = true;
}
dr << info << "rule " << n1 << " also matches";
}
}
if (!ambig)
{
auto g (
make_exception_guard (
[](target& t, const string& n)
{
info << "while applying rule " << n << " for target " << t;
},
t, n));
t.recipe (a, ru.apply (a, t, m));
break;
}
else
dr << info << "use rule hint to disambiguate this match";
}
}
}
if (!t.recipe (a))
fail << "no rule to update target " << t;
}
void
search_and_match (action a, target& t)
{
for (prerequisite& p: t.prerequisites)
{
if (p.target == nullptr)
search (p);
match (a, *p.target);
}
}
target_state
execute (action a, target& t)
{
// Implementation with some multi-threading ideas in mind.
//
switch (target_state ts = t.state ())
{
case target_state::unknown:
{
t.state (target_state::failed); // So the rule can just throw.
auto g (
make_exception_guard (
[](target& t){info << "while updating target " << t;},
t));
ts = t.recipe (a) (a, t);
assert (ts != target_state::unknown && ts != target_state::failed);
t.state (ts);
return ts;
}
case target_state::unchanged:
case target_state::changed:
return ts;
case target_state::failed:
throw failed ();
}
}
target_state
execute_prerequisites (action a, target& t)
{
target_state ts (target_state::unchanged);
for (const prerequisite& p: t.prerequisites)
{
assert (p.target != nullptr);
if (execute (a, *p.target) != target_state::unchanged)
ts = target_state::changed;
}
return ts;
}
bool
execute_prerequisites (action a, target& t, const timestamp& mt)
{
bool e (mt == timestamp_nonexistent);
for (const prerequisite& p: t.prerequisites)
{
assert (p.target != nullptr);
target& pt (*p.target);
target_state ts (execute (a, pt));
if (!e)
{
// If this is an mtime-based target, then compare timestamps.
//
if (auto mpt = dynamic_cast<const mtime_target*> (&pt))
{
timestamp mp (mpt->mtime ());
// What do we do if timestamps are equal? This can happen, for
// example, on filesystems that don't have subsecond resolution.
// There is not much we can do here except detect the case where
// the prerequisite was changed in this run which means the
// action must be executed on the target as well.
//
if (mt < mp || (mt == mp && ts == target_state::changed))
e = true;
}
else
{
// Otherwise we assume the prerequisite is newer if it was changed.
//
if (ts == target_state::changed)
e = true;
}
}
}
return e;
}
}
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