From 5dfea34048aa8541f20aeb2fbcd163561b609a49 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Thu, 2 Jul 2015 22:51:33 +0200
Subject: [PATCH] Use std::vector::data()

---
 nix/libstore/build.cc |  7 ++-----
 nix/libutil/util.cc   | 11 +++++------
 nix/libutil/util.hh   |  2 +-
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/nix/libstore/build.cc b/nix/libstore/build.cc
index 11ca6cfe08..7159d7b4c4 100644
--- a/nix/libstore/build.cc
+++ b/nix/libstore/build.cc
@@ -2174,7 +2174,6 @@ void DerivationGoal::runChild()
         Strings envStrs;
         foreach (Environment::const_iterator, i, env)
             envStrs.push_back(rewriteHashes(i->first + "=" + i->second, rewritesToTmp));
-        auto envArr = stringsToCharPtrs(envStrs);
 
         /* If we are running in `build-users' mode, then switch to the
            user we allocated above.  Make sure that we drop all root
@@ -2205,7 +2204,6 @@ void DerivationGoal::runChild()
         args.push_back(builderBasename);
         foreach (Strings::iterator, i, drv.args)
             args.push_back(rewriteHashes(*i, rewritesToTmp));
-        auto argArr = stringsToCharPtrs(args);
 
         restoreSIGPIPE();
 
@@ -2213,7 +2211,7 @@ void DerivationGoal::runChild()
         writeFull(STDERR_FILENO, "\n");
 
         /* Execute the program.  This should not return. */
-        execve(drv.builder.c_str(), (char * *) &argArr[0], (char * *) &envArr[0]);
+        execve(drv.builder.c_str(), stringsToCharPtrs(args).data(), stringsToCharPtrs(envStrs).data());
 
         throw SysError(format("executing `%1%'") % drv.builder);
 
@@ -2843,7 +2841,6 @@ void SubstitutionGoal::tryToRun()
     args.push_back("--substitute");
     args.push_back(storePath);
     args.push_back(destPath);
-    auto argArr = stringsToCharPtrs(args);
 
     /* Fork the substitute program. */
     pid = startProcess([&]() {
@@ -2853,7 +2850,7 @@ void SubstitutionGoal::tryToRun()
         if (dup2(outPipe.writeSide, STDOUT_FILENO) == -1)
             throw SysError("cannot dup output pipe into stdout");
 
-        execv(sub.c_str(), (char * *) &argArr[0]);
+        execv(sub.c_str(), stringsToCharPtrs(args).data());
 
         throw SysError(format("executing `%1%'") % sub);
     });
diff --git a/nix/libutil/util.cc b/nix/libutil/util.cc
index dab4235b04..14026ab829 100644
--- a/nix/libutil/util.cc
+++ b/nix/libutil/util.cc
@@ -897,10 +897,10 @@ pid_t startProcess(std::function<void()> fun,
 }
 
 
-std::vector<const char *> stringsToCharPtrs(const Strings & ss)
+std::vector<char *> stringsToCharPtrs(const Strings & ss)
 {
-    std::vector<const char *> res;
-    for (auto & s : ss) res.push_back(s.c_str());
+    std::vector<char *> res;
+    for (auto & s : ss) res.push_back((char *) s.c_str());
     res.push_back(0);
     return res;
 }
@@ -921,12 +921,11 @@ string runProgram(Path program, bool searchPath, const Strings & args)
 
         Strings args_(args);
         args_.push_front(program);
-        auto cargs = stringsToCharPtrs(args_);
 
         if (searchPath)
-            execvp(program.c_str(), (char * *) &cargs[0]);
+            execvp(program.c_str(), stringsToCharPtrs(args_).data());
         else
-            execv(program.c_str(), (char * *) &cargs[0]);
+            execv(program.c_str(), stringsToCharPtrs(args_).data());
 
         throw SysError(format("executing `%1%'") % program);
     });
diff --git a/nix/libutil/util.hh b/nix/libutil/util.hh
index 6a84ed8851..24e16ba36a 100644
--- a/nix/libutil/util.hh
+++ b/nix/libutil/util.hh
@@ -284,7 +284,7 @@ MakeError(ExecError, Error)
 /* Convert a list of strings to a null-terminated vector of char
    *'s. The result must not be accessed beyond the lifetime of the
    list of strings. */
-std::vector<const char *> stringsToCharPtrs(const Strings & ss);
+std::vector<char *> stringsToCharPtrs(const Strings & ss);
 
 /* Close all file descriptors except stdin, stdout, stderr, and those
    listed in the given set.  Good practice in child processes. */