lix/src/eval.cc

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#include <map>
#include <iostream>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
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#include <fcntl.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(const string & path)
{
int res;
struct stat st;
res = stat(path.c_str(), &st);
if (!res) return true;
if (errno != ENOENT)
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throw SysError(format("getting status of %1%") % path);
return false;
}
/* Run a program. */
static void runProgram(const string & program, Environment env)
{
/* Create a log file. */
string logFileName = nixLogDir + "/run.log";
/* !!! auto-pclose on exit */
FILE * logFile = popen(("tee " + logFileName + " >&2").c_str(), "w"); /* !!! escaping */
if (!logFile)
throw SysError(format("unable to create log file %1%") % logFileName);
/* 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 SysError("cannot pipe standard error into log file");
/* Dup stderr to stdin. */
if (dup2(STDERR_FILENO, STDOUT_FILENO) == -1)
throw SysError("cannot dup stderr into stdout");
/* Make the program executable. !!! hack. */
if (chmod(program.c_str(), 0755))
throw SysError("cannot make program executable");
/* Execute the program. This should not return. */
execle(program.c_str(), baseNameOf(program).c_str(), 0, env2);
throw SysError(format("unable to execute %1%") % program);
} catch (exception & e) {
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cerr << format("build error: %1%\n") % e.what();
}
_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");
}
/* Throw an exception if the given platform string is not supported by
the platform we are executing on. */
static void checkPlatform(const string & platform)
{
if (platform != thisSystem)
throw Error(format("a `%1%' is required, but I am a `%2%'")
% platform % thisSystem);
}
string printTerm(ATerm t)
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{
char * s = ATwriteToString(t);
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return s;
}
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Error badTerm(const format & f, ATerm t)
{
return Error(format("%1%, in `%2%'") % f.str() % printTerm(t));
}
Hash hashTerm(ATerm t)
{
return hashString(printTerm(t));
}
struct RStatus
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{
/* !!! the comparator of this hash should match the semantics of
the file system */
// map<string, Hash> paths;
};
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static ATerm termFromHash(const Hash & hash)
{
string path = queryFromStore(hash);
ATerm t = ATreadFromNamedFile(path.c_str());
if (!t) throw Error(format("cannot read aterm %1%") % path);
return t;
}
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Hash writeTerm(ATerm t)
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{
string path = nixStore + "/tmp.nix"; /* !!! */
if (!ATwriteToNamedTextFile(t, path.c_str()))
throw Error(format("cannot write aterm %1%") % path);
Hash hash = hashPath(path);
string path2 = nixStore + "/" + (string) hash + ".nix";
if (rename(path.c_str(), path2.c_str()) == -1)
throw SysError(format("renaming %1% to %2%") % path % path2);
setDB(nixDB, dbRefs, hash, path2);
return hash;
}
static FState realise(RStatus & status, FState fs)
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{
char * s1, * s2, * s3;
Content content;
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ATermList refs, ins, bnds;
/* First repeatedly try to substitute $fs$ by any known successors
in order to speed up the rewrite process. */
{
string fsHash, scHash;
while (queryDB(nixDB, dbSuccessors, fsHash = hashTerm(fs), scHash)) {
debug(format("successor %1% -> %2%") % (string) fsHash % scHash);
FState fs2 = termFromHash(parseHash(scHash));
if (fs == fs2) {
debug(format("successor cycle detected in %1%") % printTerm(fs));
break;
}
fs = fs2;
}
}
/* Fall through. */
if (ATmatch(fs, "Include(<str>)", &s1)) {
return realise(status, termFromHash(parseHash(s1)));
}
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else if (ATmatch(fs, "Path(<str>, <term>, [<list>])", &s1, &content, &refs)) {
string path(s1);
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msg(format("realising atomic path %1%") % path);
Nest nest(true);
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if (path[0] != '/')
throw Error(format("path `%1% is not absolute") % path);
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/* Realise referenced paths. */
ATermList refs2 = ATempty;
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while (!ATisEmpty(refs)) {
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refs2 = ATinsert(refs2, realise(status, ATgetFirst(refs)));
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refs = ATgetNext(refs);
}
refs2 = ATreverse(refs2);
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if (!ATmatch(content, "Hash(<str>)", &s1))
throw badTerm("hash expected", content);
Hash hash = parseHash(s1);
/* Normal form. */
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ATerm nf = ATmake("Path(<str>, <term>, <term>)",
path.c_str(), content, refs2);
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/* Register the normal form. */
if (fs != nf) {
Hash nfHash = writeTerm(nf);
setDB(nixDB, dbSuccessors, hashTerm(fs), nfHash);
}
/* Perhaps the path already exists and has the right hash? */
if (pathExists(path)) {
if (hash == hashPath(path)) {
debug(format("path %1% already has hash %2%")
% path % (string) hash);
return nf;
}
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throw Error(format("path %1% exists, but does not have hash %2%")
% path % (string) hash);
}
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/* Do we know a path with that hash? If so, copy it. */
string path2 = queryFromStore(hash);
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copyPath(path2, path);
return nf;
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}
else if (ATmatch(fs, "Derive(<str>, <str>, [<list>], <str>, [<list>])",
&s1, &s2, &ins, &s3, &bnds))
{
string platform(s1), builder(s2), outPath(s3);
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msg(format("realising derivate path %1%") % outPath);
Nest nest(true);
checkPlatform(platform);
/* Realise inputs. */
ATermList ins2 = ATempty;
while (!ATisEmpty(ins)) {
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ins2 = ATinsert(ins2, realise(status, ATgetFirst(ins)));
ins = ATgetNext(ins);
}
ins2 = ATreverse(ins2);
/* Build the environment. */
Environment env;
while (!ATisEmpty(bnds)) {
ATerm bnd = ATgetFirst(bnds);
if (!ATmatch(bnd, "(<str>, <str>)", &s1, &s2))
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throw badTerm("tuple of strings expected", bnd);
env[s1] = s2;
bnds = ATgetNext(bnds);
}
/* Check whether the target already exists. */
if (pathExists(outPath))
deleteFromStore(outPath);
// throw Error(format("path %1% already exists") % outPath);
/* Run the builder. */
runProgram(builder, env);
/* Check whether the result was created. */
if (!pathExists(outPath))
throw Error(format("program %1% failed to create a result in %2%")
% builder % outPath);
#if 0
/* 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);
#endif
/* Hash the result. */
Hash outHash = hashPath(outPath);
/* Register targetHash -> targetPath. !!! this should be in
values.cc. */
setDB(nixDB, dbRefs, outHash, outPath);
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/* Register the normal form of fs. */
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FState nf = ATmake("Path(<str>, Hash(<str>), <term>)",
outPath.c_str(), ((string) outHash).c_str(), ins2);
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Hash nfHash = writeTerm(nf);
setDB(nixDB, dbSuccessors, hashTerm(fs), nfHash);
return nf;
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}
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throw badTerm("bad fstate expression", fs);
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}
FState realiseFState(FState fs)
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{
RStatus status;
return realise(status, fs);
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}