diff --git a/builtin_set.cpp b/builtin_set.cpp
index c916d6864..454f35e71 100644
--- a/builtin_set.cpp
+++ b/builtin_set.cpp
@@ -65,7 +65,7 @@ static int my_env_set(const wchar_t *key, const wcstring_list_t &val, int scope)
     if (is_path_variable(key))
     {
         /* Fix for https://github.com/fish-shell/fish-shell/issues/199 . Return success if any path setting succeeds. */
-        bool any_success = false, any_error = false;
+        bool any_success = false;
 
         for (i=0; i< val.size() ; i++)
         {
@@ -93,7 +93,6 @@ static int my_env_set(const wchar_t *key, const wcstring_list_t &val, int scope)
             }
             else
             {
-                any_error = true;
                 const wchar_t *colon;
                 append_format(stderr_buffer, _(BUILTIN_SET_PATH_ERROR), L"set", dir, key);
                 colon = wcschr(dir, L':');
diff --git a/env_universal.cpp b/env_universal.cpp
index 2ef1c7c56..f39a608fa 100644
--- a/env_universal.cpp
+++ b/env_universal.cpp
@@ -80,7 +80,7 @@ static int is_dead()
 
 static int try_get_socket_once(void)
 {
-    int s, len;
+    int s;
 
     wchar_t *wdir;
     wchar_t *wuname;
@@ -128,7 +128,6 @@ static int try_get_socket_once(void)
     struct sockaddr_un local = {};
     local.sun_family = AF_UNIX;
     strncpy(local.sun_path, name.c_str(), (sizeof local.sun_path) - 1);
-    len = sizeof(local);
 
     if (connect(s, (struct sockaddr *)&local, sizeof local) == -1)
     {
diff --git a/exec.cpp b/exec.cpp
index 2704db683..e9841ed07 100644
--- a/exec.cpp
+++ b/exec.cpp
@@ -124,13 +124,14 @@ void exec_close(int fd)
 
 int exec_pipe(int fd[2])
 {
+    ASSERT_IS_MAIN_THREAD();
+    
     int res;
-
     while ((res=pipe(fd)))
     {
         if (errno != EINTR)
         {
-            wperror(L"pipe");
+            // caller will call wperror
             return res;
         }
     }
@@ -148,6 +149,17 @@ int exec_pipe(int fd[2])
     return res;
 }
 
+void print_open_fds(void)
+{
+    for (size_t i=0; i < open_fds.size(); ++i)
+    {
+        if (open_fds.at(i))
+        {
+            fprintf(stderr, "fd %lu\n", i);
+        }
+    }
+}
+
 /**
    Check if the specified fd is used as a part of a pipeline in the
    specidied set of IO redirections.
@@ -526,9 +538,7 @@ static bool can_use_posix_spawn_for_job(const job_t *job, const process_t *proce
 
 void exec(parser_t &parser, job_t *j)
 {
-    process_t *p;
     pid_t pid = 0;
-    int mypipe[2];
     sigset_t chldset;
 
     shared_ptr<io_buffer_t> io_buffer;
@@ -559,10 +569,10 @@ void exec(parser_t &parser, job_t *j)
         j->io.insert(j->io.begin(), parser.block_io.begin(), parser.block_io.end());
     }
 
-    const io_buffer_t *input_redirect = 0;
+    const io_buffer_t *input_redirect = NULL;
     for (size_t idx = 0; idx < j->io.size(); idx++)
     {
-        shared_ptr<io_data_t> &io = j->io.at(idx);
+        const shared_ptr<io_data_t> &io = j->io.at(idx);
 
         if ((io->io_mode == IO_BUFFER))
         {
@@ -611,12 +621,13 @@ void exec(parser_t &parser, job_t *j)
         }
 
     }
-
+    
+    // This is a pipe that the "current" process in our loop below reads from
+    // Only pipe_read->pipe_fd[0] is used
     shared_ptr<io_pipe_t> pipe_read(new io_pipe_t(0, true));
-    pipe_read->pipe_fd[0] = pipe_read->pipe_fd[1] = -1;
-
+    
+    // This is the pipe that the "current" process in our loop below writes to
     shared_ptr<io_pipe_t> pipe_write(new io_pipe_t(1, false));
-    pipe_write->pipe_fd[0] = pipe_write->pipe_fd[1] = -1;
 
     j->io.push_back(pipe_write);
 
@@ -634,7 +645,7 @@ void exec(parser_t &parser, job_t *j)
 
     if (job_get_flag(j, JOB_CONTROL))
     {
-        for (p=j->first_process; p; p = p->next)
+        for (const process_t *p = j->first_process; p; p = p->next)
         {
             if (p->type != EXTERNAL)
             {
@@ -676,7 +687,10 @@ void exec(parser_t &parser, job_t *j)
             set_child_group(j, &keepalive, 0);
         }
     }
-
+    
+    /* Make a set of file descriptors that we will need to close */
+    std::set<int> fds_to_close;
+    
     /*
       This loop loops over every process_t in the job, starting it as
       appropriate. This turns out to be rather complex, since a
@@ -685,10 +699,10 @@ void exec(parser_t &parser, job_t *j)
       The loop also has to handle pipelining between the jobs.
     */
 
-    for (p=j->first_process; p; p = p->next)
+    for (process_t *p=j->first_process; p; p = p->next)
     {
         const bool p_wants_pipe = (p->next != NULL);
-        mypipe[1]=-1;
+        int mypipe[2] = {-1, -1};
 
         pipe_write->fd = p->pipe_write_fd;
         pipe_read->fd = p->pipe_read_fd;
@@ -714,6 +728,7 @@ void exec(parser_t &parser, job_t *j)
 
         if (p == j->first_process->next)
         {
+            /* We are the first process that could possibly read from a pipe (aka the second process), so add the pipe read redireciton */
             j->io.push_back(pipe_read);
         }
 
@@ -726,9 +741,14 @@ void exec(parser_t &parser, job_t *j)
                 debug(1, PIPE_ERROR);
                 wperror(L"pipe");
                 exec_error = true;
+                job_mark_process_as_failed(j, p);
                 break;
             }
-
+            
+            fds_to_close.insert(mypipe[0]);
+            fds_to_close.insert(mypipe[1]);
+            
+            // This tells the redirection about the fds, but the redirection does not close them
             memcpy(pipe_write->pipe_fd, mypipe, sizeof(int)*2);
         }
         else
@@ -746,7 +766,6 @@ void exec(parser_t &parser, job_t *j)
         {
             case INTERNAL_FUNCTION:
             {
-                wchar_t * def=0;
                 int shadows;
 
 
@@ -757,20 +776,15 @@ void exec(parser_t &parser, job_t *j)
                 */
 
                 signal_unblock();
-                wcstring orig_def;
-                function_get_definition(p->argv0(), &orig_def);
-
-                // function_get_named_arguments may trigger autoload, which deallocates the orig_def.
-                // We should make function_get_definition return a wcstring (but how to handle NULL...)
-                if (! orig_def.empty())
-                    def = wcsdup(orig_def.c_str());
+                wcstring def;
+                bool function_exists = function_get_definition(p->argv0(), &def);
 
                 wcstring_list_t named_arguments = function_get_named_arguments(p->argv0());
                 shadows = function_get_shadows(p->argv0());
 
                 signal_block();
 
-                if (def == NULL)
+                if (! function_exists)
                 {
                     debug(0, _(L"Unknown function '%ls'"), p->argv0());
                     break;
@@ -778,7 +792,6 @@ void exec(parser_t &parser, job_t *j)
                 function_block_t *newv = new function_block_t(p, p->argv0(), shadows);
                 parser.push_block(newv);
 
-
                 /*
                   set_argv might trigger an event
                   handler, hence we need to unblock
@@ -792,15 +805,26 @@ void exec(parser_t &parser, job_t *j)
 
                 if (p->next)
                 {
+                    // Be careful to handle failure, e.g. too many open fds
                     io_buffer.reset(io_buffer_t::create(0));
-                    j->io.push_back(io_buffer);
+                    if (io_buffer.get() == NULL)
+                    {
+                        exec_error = true;
+                        job_mark_process_as_failed(j, p);
+                    }
+                    else
+                    {
+                        j->io.push_back(io_buffer);
+                    }
+                }
+                
+                if (! exec_error)
+                {
+                    internal_exec_helper(parser, def.c_str(), TOP, j->io);
                 }
-
-                internal_exec_helper(parser, def, TOP, j->io);
 
                 parser.allow_function();
                 parser.pop_block();
-                free(def);
 
                 break;
             }
@@ -810,10 +834,21 @@ void exec(parser_t &parser, job_t *j)
                 if (p->next)
                 {
                     io_buffer.reset(io_buffer_t::create(0));
-                    j->io.push_back(io_buffer);
+                    if (io_buffer.get() == NULL)
+                    {
+                        exec_error = true;
+                        job_mark_process_as_failed(j, p);
+                    }
+                    else
+                    {
+                        j->io.push_back(io_buffer);
+                    }
+                }
+                
+                if (! exec_error)
+                {
+                    internal_exec_helper(parser, p->argv0(), TOP, j->io);
                 }
-
-                internal_exec_helper(parser, p->argv0(), TOP, j->io);
                 break;
 
             }
@@ -821,7 +856,6 @@ void exec(parser_t &parser, job_t *j)
             case INTERNAL_BUILTIN:
             {
                 int builtin_stdin=0;
-                int fg;
                 int close_stdin=0;
 
                 /*
@@ -933,7 +967,7 @@ void exec(parser_t &parser, job_t *j)
                     builtin_out_redirect = has_fd(j->io, 1);
                     builtin_err_redirect = has_fd(j->io, 2);
 
-                    fg = job_get_flag(j, JOB_FOREGROUND);
+                    const int fg = job_get_flag(j, JOB_FOREGROUND);
                     job_set_flag(j, JOB_FOREGROUND, 0);
 
                     signal_unblock();
@@ -1300,6 +1334,11 @@ void exec(parser_t &parser, job_t *j)
                           safe_launch_process _never_ returns...
                         */
                     }
+                    else if (pid < 0)
+                    {
+                        job_mark_process_as_failed(j, p);
+                        exec_error = true;
+                    }
                 }
 
 
@@ -1325,24 +1364,29 @@ void exec(parser_t &parser, job_t *j)
            previous process_t
         */
         if (pipe_read->pipe_fd[0] >= 0)
+        {
             exec_close(pipe_read->pipe_fd[0]);
+            fds_to_close.erase(pipe_read->pipe_fd[0]);
+        }
         /*
            Set up the pipe the next process uses to read from the
            current process_t
         */
         if (p_wants_pipe)
+        {
+            /* The next process will read from this pipe */
+            assert(p->next != NULL);
             pipe_read->pipe_fd[0] = mypipe[0];
 
-        /*
-           If there is a next process in the pipeline, close the
-           output end of the current pipe (the surrent child
-           subprocess already has a copy of the pipe - this makes sure
-           we don't leak file descriptors either in the shell or in
-           the children).
-        */
-        if (p->next)
-        {
+            /*
+               If there is a next process in the pipeline, close the
+               output end of the current pipe (the current child
+               subprocess already has a copy of the pipe - this makes sure
+               we don't leak file descriptors either in the shell or in
+               the children).
+            */
             exec_close(mypipe[1]);
+            fds_to_close.erase(mypipe[1]);
         }
     }
 
@@ -1354,6 +1398,11 @@ void exec(parser_t &parser, job_t *j)
     {
         kill(keepalive.pid, SIGKILL);
     }
+    
+    for (std::set<int>::iterator foo = fds_to_close.begin(); foo != fds_to_close.end(); ++foo)
+    {
+        fprintf(stderr, "-Malingering %d\n", *foo);
+    }
 
     signal_unblock();
 
@@ -1368,9 +1417,14 @@ void exec(parser_t &parser, job_t *j)
         proc_last_bg_pid = j->pgid;
     }
 
-    if (!exec_error)
+    if (! exec_error)
     {
-        job_continue(j, 0);
+        job_continue(j, false);
+    }
+    else
+    {
+        /* Mark the errored job as not in the foreground. I can't fully justify whether this is the right place, but it prevents sanity_lose from complaining. */
+        job_set_flag(j, JOB_FOREGROUND, 0);
     }
 
 }
@@ -1401,27 +1455,35 @@ static int exec_subshell_internal(const wcstring &cmd, wcstring_list_t *lst)
 
     is_subshell=1;
 
-    const shared_ptr<io_buffer_t> io_buffer(io_buffer_t::create(0));
-
     prev_status = proc_get_last_status();
 
-    parser_t &parser = parser_t::principal_parser();
-    if (parser.eval(cmd, io_chain_t(io_buffer), SUBST))
+    const shared_ptr<io_buffer_t> io_buffer(io_buffer_t::create(0));
+    
+    // IO buffer creation may fail (e.g. if we have too many open files to make a pipe), so this may be null
+    if (io_buffer.get() == NULL)
     {
         status = -1;
     }
     else
     {
-        status = proc_get_last_status();
+        parser_t &parser = parser_t::principal_parser();
+        if (parser.eval(cmd, io_chain_t(io_buffer), SUBST))
+        {
+            status = -1;
+        }
+        else
+        {
+            status = proc_get_last_status();
+        }
+        
+        io_buffer->read();
     }
 
-    io_buffer->read();
-
     proc_set_last_status(prev_status);
 
     is_subshell = prev_subshell;
 
-    if (lst != NULL)
+    if (lst != NULL && io_buffer.get() != NULL)
     {
         const char *begin = io_buffer->out_buffer_ptr();
         const char *end = begin + io_buffer->out_buffer_size();
diff --git a/io.cpp b/io.cpp
index f6947cb21..f1d664f8f 100644
--- a/io.cpp
+++ b/io.cpp
@@ -156,6 +156,10 @@ io_buffer_t *io_buffer_t::create(bool is_input)
         delete buffer_redirect;
         buffer_redirect = NULL;
     }
+    else
+    {
+        //fprintf(stderr, "Created pipes {%d, %d} for %p\n", buffer_redirect->pipe_fd[0], buffer_redirect->pipe_fd[1], buffer_redirect);
+    }
 
     return buffer_redirect;
 }
@@ -163,16 +167,20 @@ io_buffer_t *io_buffer_t::create(bool is_input)
 io_buffer_t::~io_buffer_t()
 {
 
+    //fprintf(stderr, "Deallocating pipes {%d, %d} for %p\n", this->pipe_fd[0], this->pipe_fd[1], this);
     /**
        If this is an input buffer, then io_read_buffer will not have
        been called, and we need to close the output fd as well.
     */
-    if (is_input)
+    if (is_input && pipe_fd[1] >= 0)
     {
         exec_close(pipe_fd[1]);
     }
 
-    exec_close(pipe_fd[0]);
+    if (pipe_fd[0] >= 0)
+    {
+        exec_close(pipe_fd[0]);
+    }
 
     /*
       Dont free fd for writing. This should already be free'd before
@@ -193,6 +201,13 @@ void io_chain_t::remove(const shared_ptr<const io_data_t> &element)
     }
 }
 
+void io_chain_t::push_back(const shared_ptr<io_data_t> &element)
+{
+    // Ensure we never push back NULL
+    assert(element.get() != NULL);
+    std::vector<shared_ptr<io_data_t> >:: push_back(element);
+}
+
 void io_remove(io_chain_t &list, const shared_ptr<const io_data_t> &element)
 {
     list.remove(element);
diff --git a/io.h b/io.h
index 2a1999c9c..b007bbf65 100644
--- a/io.h
+++ b/io.h
@@ -95,22 +95,22 @@ class io_pipe_t : public io_data_t
 protected:
     io_pipe_t(io_mode_t m, int f, bool i):
         io_data_t(m, f),
-        pipe_fd(),
         is_input(i)
     {
+        pipe_fd[0] = pipe_fd[1] = -1;
     }
 
 public:
     int pipe_fd[2];
-    bool is_input;
+    const bool is_input;
 
     virtual void print() const;
 
     io_pipe_t(int f, bool i):
         io_data_t(IO_PIPE, f),
-        pipe_fd(),
         is_input(i)
     {
+        pipe_fd[0] = pipe_fd[1] = -1;
     }
 };
 
@@ -178,6 +178,7 @@ public:
     io_chain_t(const shared_ptr<io_data_t> &);
 
     void remove(const shared_ptr<const io_data_t> &element);
+    void push_back(const shared_ptr<io_data_t> &element);
 
     shared_ptr<const io_data_t> get_io_for_fd(int fd) const;
     shared_ptr<io_data_t> get_io_for_fd(int fd);
diff --git a/parser.cpp b/parser.cpp
index ca524b8db..c0ff3a7dd 100644
--- a/parser.cpp
+++ b/parser.cpp
@@ -1202,11 +1202,14 @@ bool parser_t::job_remove(job_t *j)
 
 void parser_t::job_promote(job_t *job)
 {
+    signal_block();
+    
     job_list_t::iterator loc = std::find(my_job_list.begin(), my_job_list.end(), job);
     assert(loc != my_job_list.end());
 
     /* Move the job to the beginning */
     my_job_list.splice(my_job_list.begin(), my_job_list, loc);
+    signal_unblock();
 }
 
 job_t *parser_t::job_get(job_id_t id)
@@ -3755,7 +3758,7 @@ event_block_t::event_block_t(const event_t &evt) :
 {
 }
 
-function_block_t::function_block_t(process_t *p, const wcstring &n, bool shadows) :
+function_block_t::function_block_t(const process_t *p, const wcstring &n, bool shadows) :
     block_t(shadows ? FUNCTION_CALL : FUNCTION_CALL_NO_SHADOW),
     process(p),
     name(n)
diff --git a/parser.h b/parser.h
index 7677754b3..c2ad6c9b7 100644
--- a/parser.h
+++ b/parser.h
@@ -164,9 +164,9 @@ struct event_block_t : public block_t
 
 struct function_block_t : public block_t
 {
-    process_t *process;
+    const process_t *process;
     wcstring name;
-    function_block_t(process_t *p, const wcstring &n, bool shadows);
+    function_block_t(const process_t *p, const wcstring &n, bool shadows);
 };
 
 struct source_block_t : public block_t
diff --git a/proc.cpp b/proc.cpp
index 1ed63b5eb..fe9c3d41f 100644
--- a/proc.cpp
+++ b/proc.cpp
@@ -117,6 +117,15 @@ job_iterator_t::job_iterator_t() : job_list(&parser_t::principal_parser().job_li
     this->reset();
 }
 
+void print_jobs(void)
+{
+    job_iterator_t jobs;
+    job_t *j;
+    while ((j = jobs.next()))
+    {
+        printf("%p -> %ls -> (foreground %d, complete %d, stopped %d, constructed %d)\n", j, j->command_wcstr(), job_get_flag(j, JOB_FOREGROUND), job_is_completed(j), job_is_stopped(j), job_get_flag(j, JOB_CONSTRUCTED));
+    }
+}
 
 int is_interactive_session=0;
 int is_subshell=0;
@@ -305,17 +314,21 @@ int job_is_completed(const job_t *j)
 
 }
 
-void job_set_flag(job_t *j, int flag, int set)
+void job_set_flag(job_t *j, unsigned int flag, int set)
 {
     if (set)
+    {
         j->flags |= flag;
+    }
     else
-        j->flags = j->flags & ((unsigned int)(-1) ^ flag);
+    {
+        j->flags &= ~flag;
+    }
 }
 
-int job_get_flag(const job_t *j, int flag)
+int job_get_flag(const job_t *j, unsigned int flag)
 {
-    return j->flags&flag?1:0;
+    return !! (j->flags & flag);
 }
 
 int job_signal(job_t *j, int signal)
@@ -396,7 +409,10 @@ static void mark_process_status(const job_t *j,
 void job_mark_process_as_failed(const job_t *job, process_t *p)
 {
     /* The given process failed to even lift off (e.g. posix_spawn failed) and so doesn't have a valid pid. Mark it as dead. */
-    p->completed = 1;
+    for (process_t *cursor = p; p != NULL; p = p->next)
+    {
+        cursor->completed = 1;
+    }
 }
 
 /**
@@ -630,7 +646,6 @@ int job_reap(bool interactive)
     {
         job_t *j = jnext;
         jnext = jobs.next();
-        process_t *p;
 
         /*
           If we are reaping only jobs who do not need status messages
@@ -642,7 +657,7 @@ int job_reap(bool interactive)
             continue;
         }
 
-        for (p=j->first_process; p; p=p->next)
+        for (process_t *p = j->first_process; p; p=p->next)
         {
             int s;
             if (!p->completed)
@@ -902,7 +917,7 @@ static int select_try(job_t *j)
 */
 static void read_try(job_t *j)
 {
-    io_buffer_t *buff=NULL;
+    io_buffer_t *buff = NULL;
 
     /*
       Find the last buffer, which is the one we want to read from
@@ -1030,7 +1045,7 @@ static int terminal_return_from_job(job_t *j)
     return 1;
 }
 
-void job_continue(job_t *j, int cont)
+void job_continue(job_t *j, bool cont)
 {
     /*
       Put job first in the job list
diff --git a/proc.h b/proc.h
index a97ccbd92..2d09b7518 100644
--- a/proc.h
+++ b/proc.h
@@ -141,9 +141,9 @@ private:
 public:
 
     process_t();
-
     ~process_t();
 
+
     /**
       Type of process. Can be one of \c EXTERNAL, \c
       INTERNAL_BUILTIN, \c INTERNAL_FUNCTION, \c INTERNAL_BLOCK,
@@ -453,12 +453,12 @@ extern int no_exec;
 /**
    Add the specified flag to the bitset of flags for the specified job
  */
-void job_set_flag(job_t *j, int flag, int set);
+void job_set_flag(job_t *j, unsigned int flag, int set);
 
 /**
    Returns one if the specified flag is set in the specified job, 0 otherwise.
  */
-int job_get_flag(const job_t *j, int flag);
+int job_get_flag(const job_t *j, unsigned int flag);
 
 /**
    Sets the status of the last process to exit
@@ -515,7 +515,7 @@ int job_is_completed(const job_t *j);
   \param j The job
   \param cont Whether the function should wait for the job to complete before returning
 */
-void job_continue(job_t *j, int cont);
+void job_continue(job_t *j, bool cont);
 
 /**
    Notify the user about stopped or terminated jobs. Delete terminated
diff --git a/reader.cpp b/reader.cpp
index ae8c9b224..d0312c2d3 100644
--- a/reader.cpp
+++ b/reader.cpp
@@ -1048,6 +1048,13 @@ static void run_pager(const wcstring &prefix, int is_quoted, const std::vector<c
     wcstring msg;
     wcstring prefix_esc;
     char *foo;
+    
+    shared_ptr<io_buffer_t> in(io_buffer_t::create(true));
+    shared_ptr<io_buffer_t> out(io_buffer_t::create(false));
+    
+    // The above may fail e.g. if we have too many open fds
+    if (in.get() == NULL || out.get() == NULL)
+        return;
 
     wchar_t *escaped_separator;
     int has_case_sensitive=0;
@@ -1066,7 +1073,6 @@ static void run_pager(const wcstring &prefix, int is_quoted, const std::vector<c
                                  is_quoted?L"-q":L"",
                                  prefix_esc.c_str());
 
-    shared_ptr<io_buffer_t> in(io_buffer_t::create(true));
     in->fd = 3;
 
     escaped_separator = escape(COMPLETE_SEP_STR, 1);
@@ -1133,11 +1139,9 @@ static void run_pager(const wcstring &prefix, int is_quoted, const std::vector<c
     in->out_buffer_append(foo, strlen(foo));
     free(foo);
 
-    term_donate();
-
-    shared_ptr<io_buffer_t> out(io_buffer_t::create(false));
     out->fd = 4;
-
+    
+    term_donate();
     parser_t &parser = parser_t::principal_parser();
     io_chain_t io_chain;
     io_chain.push_back(out);