diff options
Diffstat (limited to 'libbuild2/rule.cxx')
| -rw-r--r-- | libbuild2/rule.cxx | 71 |
1 files changed, 57 insertions, 14 deletions
diff --git a/libbuild2/rule.cxx b/libbuild2/rule.cxx index 5e28805..b9441e0 100644 --- a/libbuild2/rule.cxx +++ b/libbuild2/rule.cxx @@ -490,26 +490,69 @@ namespace build2 if (dd.expect ("adhoc 1") != nullptr) l4 ([&]{trace << "rule mismatch forcing update of " << t;}); - // Then the tool checksums. + // Then the script checksum. // - // @@ TODO: obtain checksums of all the targets used as commands in - // the script. + // Ideally, to detect changes to the script semantics, we would hash the + // text with all the variables expanded but without executing any + // commands. In practice, this is easier said than done (think the set + // builtin that receives output of a command that modifies the + // filesystem). // - //if (dd.expect (csum) != nullptr) - // l4 ([&]{trace << "compiler mismatch forcing update of " << t;}); + // So as the next best thing we are going to hash the unexpanded text as + // well as values of all the variables expanded in it (which we get as a + // side effect of pre-parsing the script). This approach has a number of + // drawbacks: + // + // - We can't handle computed variable names (e.g., $($x ? X : Y)). + // + // - We may "overhash" by including variables that are actually + // script-local. + // + if (dd.expect (checksum) != nullptr) + l4 ([&]{trace << "recipe text change forcing update of " << t;}); - // Then the script checksum. + // For each variable hash its name, undefined/null/non-null indicator, + // and the value if non-null. // - // @@ TODO: for now we hash the unexpanded text but it should be - // expanded. This will take care of all the relevant input - // file name changes as well as any other variables the - // script may reference. + { + sha256 cs; + names storage; + + for (const string& n: script.vars) + { + cs.append (n); + + lookup l; + + if (const variable* var = ctx.var_pool.find (n)) + l = t[var]; + + cs.append (!l.defined () ? '\x1' : l->null ? '\x2' : '\x3'); + + if (l) + { + storage.clear (); + names_view ns (reverse (*l, storage)); + + for (const name& n: ns) + to_checksum (cs, n); + } + } + + //@@ TODO (later): hash special variables values (targets, + // prerequisites). + + if (dd.expect (cs.string ()) != nullptr) + l4 ([&]{trace << "recipe variable change forcing update of " << t;}); + } + + // Then the tools checksums. // - // It feels like we need a special execute mode that instead - // of executing hashes the commands. + // @@ TODO: obtain checksums of all the targets used as commands in + // the script. // - //if (dd.expect (sha256 (code).string ()) != nullptr) - // l4 ([&]{trace << "recipe change forcing update of " << t;}); + //if (dd.expect (csum) != nullptr) + // l4 ([&]{trace << "compiler mismatch forcing update of " << t;}); } // Update if depdb mismatch. |