diff options
Diffstat (limited to 'src/eval.cc')
| -rw-r--r-- | src/eval.cc | 297 |
1 files changed, 297 insertions, 0 deletions
diff --git a/src/eval.cc b/src/eval.cc new file mode 100644 index 000000000..14577c873 --- /dev/null +++ b/src/eval.cc @@ -0,0 +1,297 @@ +#include <map> +#include <iostream> + +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/wait.h> +#include <unistd.h> + +#include "eval.hh" +#include "globals.hh" +#include "values.hh" +#include "db.hh" + + +/* A Unix environment is a mapping from strings to strings. */ +typedef map<string, string> Environment; + + +/* Return true iff the given path exists. */ +bool pathExists(string path) +{ + int res; + struct stat st; + res = stat(path.c_str(), &st); + if (!res) return true; + if (errno != ENOENT) + throw SysError("getting status of " + path); + return false; +} + + +/* Compute a derived value by running a program. */ +static Hash computeDerived(Hash sourceHash, string targetName, + string platform, Hash prog, Environment env) +{ + string targetPath = nixValues + "/" + + (string) sourceHash + "-nf"; + + /* Check whether the target already exists. */ + if (pathExists(targetPath)) + throw Error("derived value in " + targetPath + " already exists"); + + /* Find the program corresponding to the hash `prog'. */ + string progPath = queryValuePath(prog); + + /* Finalize the environment. */ + env["out"] = targetPath; + + /* Create a log file. */ + string logFileName = + nixLogDir + "/" + baseNameOf(targetPath) + ".log"; + /* !!! auto-pclose on exit */ + FILE * logFile = popen(("tee " + logFileName + " >&2").c_str(), "w"); /* !!! escaping */ + if (!logFile) + throw SysError("unable to create log file " + logFileName); + + try { + + /* Fork a child to build the package. */ + pid_t pid; + switch (pid = fork()) { + + case -1: + throw SysError("unable to fork"); + + case 0: + + try { /* child */ + +#if 0 + /* Try to use a prebuilt. */ + string prebuiltHashS, prebuiltFile; + if (queryDB(nixDB, dbPrebuilts, hash, prebuiltHashS)) { + + try { + prebuiltFile = getFile(parseHash(prebuiltHashS)); + } catch (Error e) { + cerr << "cannot obtain prebuilt (ignoring): " << e.what() << endl; + goto build; + } + + cerr << "substituting prebuilt " << prebuiltFile << endl; + + int res = system(("tar xfj " + prebuiltFile + " 1>&2").c_str()); // !!! escaping + if (WEXITSTATUS(res) != 0) + /* This is a fatal error, because path may now + have clobbered. */ + throw Error("cannot unpack " + prebuiltFile); + + _exit(0); + } +#endif + + build: + + /* Fill in the environment. We don't bother freeing + the strings, since we'll exec or die soon + anyway. */ + const char * env2[env.size() + 1]; + int i = 0; + for (Environment::iterator it = env.begin(); + it != env.end(); it++, i++) + env2[i] = (new string(it->first + "=" + it->second))->c_str(); + env2[i] = 0; + + /* Dup the log handle into stderr. */ + if (dup2(fileno(logFile), STDERR_FILENO) == -1) + throw Error("cannot pipe standard error into log file: " + string(strerror(errno))); + + /* Dup stderr to stdin. */ + if (dup2(STDERR_FILENO, STDOUT_FILENO) == -1) + throw Error("cannot dup stderr into stdout"); + + /* Make the program executable. !!! hack. */ + if (chmod(progPath.c_str(), 0755)) + throw Error("cannot make program executable"); + + /* Execute the program. This should not return. */ + execle(progPath.c_str(), baseNameOf(progPath).c_str(), 0, env2); + + throw Error("unable to execute builder: " + + string(strerror(errno))); + + } catch (exception & e) { + cerr << "build error: " << e.what() << endl; + _exit(1); + } + + } + + /* parent */ + + /* Close the logging pipe. Note that this should not cause + the logger to exit until builder exits (because the latter + has an open file handle to the former). */ + pclose(logFile); + + /* Wait for the child to finish. */ + int status; + if (waitpid(pid, &status, 0) != pid) + throw Error("unable to wait for child"); + + if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) + throw Error("unable to build package"); + + /* Check whether the result was created. */ + if (!pathExists(targetPath)) + throw Error("program " + progPath + + " failed to create a result in " + targetPath); + + /* Remove write permission from the value. */ + int res = system(("chmod -R -w " + targetPath).c_str()); // !!! escaping + if (WEXITSTATUS(res) != 0) + throw Error("cannot remove write permission from " + targetPath); + + } catch (exception &) { +// system(("rm -rf " + targetPath).c_str()); + throw; + } + + /* Hash the result. */ + Hash targetHash = hashFile(targetPath); + + /* Register targetHash -> targetPath. !!! this should be in + values.cc. */ + setDB(nixDB, dbNFs, sourceHash, targetName); + + /* Register that targetHash was produced by evaluating + sourceHash; i.e., that targetHash is a normal form of + sourceHash. !!! this shouldn't be here */ + setDB(nixDB, dbNFs, sourceHash, targetHash); + + return targetHash; +} + + +/* Throw an exception if the given platform string is not supported by + the platform we are executing on. */ +static void checkPlatform(string platform) +{ + if (platform != thisSystem) + throw Error("a `" + platform + + "' is required, but I am a `" + thisSystem + "'"); +} + + +/* Throw an exception with an error message containing the given + aterm. */ +static Error badTerm(const string & msg, Expr e) +{ + char * s = ATwriteToString(e); + return Error(msg + ", in `" + s + "'"); +} + + +/* Hash an expression. Hopefully the representation used by + ATwriteToString() won't change, otherwise all hashes will + change. */ +static Hash hashExpr(Expr e) +{ + char * s = ATwriteToString(e); + debug(s); + return hashString(s); +} + + +/* Evaluate an expression; the result must be a string. */ +static string evalString(Expr e) +{ + e = evalValue(e).e; + char * s; + if (ATmatch(e, "Str(<str>)", &s)) return s; + else throw badTerm("string value expected", e); +} + + +/* Evaluate an expression; the result must be a external + non-expression reference. */ +static Hash evalExternal(Expr e) +{ + EvalResult r = evalValue(e); + char * s; + if (ATmatch(r.e, "External(<str>)", &s)) return r.h; + else throw badTerm("external non-expression value expected", r.e); +} + + +/* Evaluate an expression. */ +EvalResult evalValue(Expr e) +{ + EvalResult r; + char * s; + Expr eBuildPlatform, eProg; + ATermList args; + + /* Normal forms. */ + if (ATmatch(e, "Str(<str>)", &s) || + ATmatch(e, "Bool(True)") || + ATmatch(e, "Bool(False)")) + { + r.e = e; + } + + /* External expressions. */ + + /* External non-expressions. */ + else if (ATmatch(e, "External(<str>)", &s)) { + r.e = e; + r.h = parseHash(s); + } + + /* Execution primitive. */ + + else if (ATmatch(e, "Exec(<term>, <term>, [<list>])", + &eBuildPlatform, &eProg, &args)) + { + string buildPlatform = evalString(eBuildPlatform); + + checkPlatform(buildPlatform); + + Hash prog = evalExternal(eProg); + + Environment env; + while (!ATisEmpty(args)) { + debug("arg"); + Expr arg = ATgetFirst(args); + throw badTerm("foo", arg); + args = ATgetNext(args); + } + + Hash sourceHash = hashExpr( + ATmake("Exec(Str(<str>), External(<str>), [])", + buildPlatform.c_str(), ((string) prog).c_str())); + + /* Do we know a normal form for sourceHash? */ + Hash targetHash; + string targetHashS; + if (queryDB(nixDB, dbNFs, sourceHash, targetHashS)) { + /* Yes. */ + targetHash = parseHash(targetHashS); + debug("already built: " + (string) sourceHash + + " -> " + (string) targetHash); + } else { + /* No, so we compute one. */ + targetHash = computeDerived(sourceHash, + (string) sourceHash + "-nf", buildPlatform, prog, env); + } + + r.e = ATmake("External(<str>)", ((string) targetHash).c_str()); + r.h = targetHash; + } + + /* Barf. */ + else throw badTerm("invalid expression", e); + + return r; +} |