close #296.

include/boost/process/detail/posix/basic_cmd.hpp

@@ -155,13 +155,15 @@ private:
 
 std::vector<char*> exe_cmd_init<char>::make_cmd()
 {
+    // any string must be writable.
+    static char empty_string[1] = "";
     std::vector<char*> vec;
     if (!exe.empty())
-        vec.push_back(&exe.front());
+        vec.push_back(exe.empty() ? empty_string : &exe.front());
 
     if (!args.empty()) {
         for (auto & v : args)
-            vec.push_back(&v.front());
+            vec.push_back(v.empty() ? empty_string : &v.front());
     }
 
     vec.push_back(nullptr);

include/boost/process/v2/ext/impl/cmd.ipp

@@ -92,13 +92,12 @@ struct make_cmd_shell_
             str_lengths += (std::strlen(*c) + 1);
         }
         // yes, not the greatest solution.
-        std::string buffer;
         res.buffer_.resize(str_lengths);
 
         res.argv_ = new char*[res.argc_ + 1];
         res.free_argv_ = +[](int argc, char ** argv) {delete[] argv;};
         res.argv_[res.argc_] = nullptr;
-        auto p = &buffer[sizeof(int) * (res.argc_) + 1];
+        auto p = &*res.buffer_.begin();
 
         for (int i = 0; i < res.argc_; i++)
         {
@@ -305,9 +304,8 @@ shell cmd(boost::process::v2::pid_type pid, boost::system::error_code & ec)
         BOOST_PROCESS_V2_ASSIGN_LAST_ERROR(ec)
         return {};
     }
-    
     auto res = make_cmd_shell_::clone(cmd);
-    procstat_freeargv(proc_stat);
+    procstat_freeargv(proc_stat.get());
     return res;
 }
     

include/boost/process/v2/ext/impl/env.ipp

@@ -342,7 +342,7 @@ env_view env(boost::process::v2::pid_type pid, boost::system::error_code & ec)
         {
           auto eno = reinterpret_cast<char**>(out);
           auto eeo = eno;
-          auto str = out +  (n * sizeof(char*)) + sizeof(char*);
+            auto str = out +  (n * sizeof(char*)) + sizeof(char*);
           e = env;
           while (*e != nullptr)
           {
@@ -351,11 +351,11 @@ env_view env(boost::process::v2::pid_type pid, boost::system::error_code & ec)
             *eno = str;
             str += len;
             eno ++;
+            e++;
           }
           *eno = nullptr;
 
           ev.handle_.reset(eeo);
-
         }
         else
             BOOST_PROCESS_V2_ASSIGN_LAST_ERROR(ec)

include/boost/process/v2/impl/shell.ipp

@@ -115,7 +115,7 @@ void shell::parse_()
 
 shell::~shell()
 {
-    if (argv_ != nullptr && free_argv_)
+    if (argv_ != nullptr && free_argv_ != nullptr)
         free_argv_(argc_, argv_);
 }
 

test/cmd_test.cpp

@@ -83,3 +83,24 @@ BOOST_AUTO_TEST_CASE(implicit)
         BOOST_TEST_MESSAGE(ec.message());
     BOOST_CHECK_EQUAL(ret, 21);
 }
+
+BOOST_AUTO_TEST_CASE(empty_cmd)
+{
+    using boost::unit_test::framework::master_test_suite;
+
+    std::error_code ec;
+
+    fs::path pth = master_test_suite().argv[1];
+    auto env = boost::this_process::environment();
+
+    auto itr = std::find_if(env.begin(), env.end(),
+    [](const bp::native_environment::entry_type & e){return boost::to_upper_copy(e.get_name()) == "PATH";});
+
+    BOOST_REQUIRE(itr != env.end());
+
+    (*itr) += fs::canonical(fs::absolute(pth.parent_path())).string();
+    BOOST_REQUIRE(itr != env.end());
+
+    bp::system("sparring_partner \"\" ", ec);
+}
+