diff --git a/src/autoload.h b/src/autoload.h
index c364a4c39..f0ad9d030 100644
--- a/src/autoload.h
+++ b/src/autoload.h
@@ -27,7 +27,7 @@ file_access_attempt_t access_file(const wcstring &path, int mode);
 
 struct autoload_function_t : public lru_node_t
 {
-    autoload_function_t(const wcstring &key) : lru_node_t(key), access(), is_loaded(false), is_placeholder(false), is_internalized(false) { }
+    explicit autoload_function_t(const wcstring &key) : lru_node_t(key), access(), is_loaded(false), is_placeholder(false), is_internalized(false) { }
     file_access_attempt_t access; /** The last access attempt */
     bool is_loaded; /** Whether we have actually loaded this function */
     bool is_placeholder; /** Whether we are a placeholder that stands in for "no such function". If this is true, then is_loaded must be false. */
diff --git a/src/builtin.cpp b/src/builtin.cpp
index a4363e4b2..b83bb82a6 100644
--- a/src/builtin.cpp
+++ b/src/builtin.cpp
@@ -2805,7 +2805,7 @@ static int builtin_read(parser_t &parser, io_streams_t &streams, wchar_t **argv)
             wcstring tokens;
             tokens.reserve(buff.size());
             bool empty = true;
-
+            
             for (wcstring_range loc = wcstring_tok(buff, ifs); loc.first != wcstring::npos; loc = wcstring_tok(buff, ifs, loc))
             {
                 if (!empty) tokens.push_back(ARRAY_SEP);
@@ -2820,7 +2820,7 @@ static int builtin_read(parser_t &parser, io_streams_t &streams, wchar_t **argv)
 
             while (i<argc)
             {
-                loc = wcstring_tok(buff, (i+1<argc) ? ifs : L"", loc);
+                loc = wcstring_tok(buff, (i+1<argc) ? ifs : wcstring(), loc);
                 env_set(argv[i], loc.first == wcstring::npos ? L"" : &buff.c_str()[loc.first], place);
 
                 ++i;
@@ -3141,7 +3141,7 @@ static int builtin_cd(parser_t &parser, io_streams_t &streams, wchar_t **argv)
     }
     else
     {
-        dir_in = argv[1];
+        dir_in = env_var_t(argv[1]);
     }
 
     bool got_cd_path = false;
diff --git a/src/builtin.h b/src/builtin.h
index 859c48745..f747eb9b6 100644
--- a/src/builtin.h
+++ b/src/builtin.h
@@ -126,7 +126,7 @@ class builtin_commandline_scoped_transient_t
 {
     size_t token;
     public:
-    builtin_commandline_scoped_transient_t(const wcstring &cmd);
+    explicit builtin_commandline_scoped_transient_t(const wcstring &cmd);
     ~builtin_commandline_scoped_transient_t();
 };
 
diff --git a/src/builtin_printf.cpp b/src/builtin_printf.cpp
index b2bcfc7c4..d5fa1d638 100644
--- a/src/builtin_printf.cpp
+++ b/src/builtin_printf.cpp
@@ -66,7 +66,7 @@ struct builtin_printf_state_t
     /* Whether we should stop outputting. This gets set in the case of an error, and also with the \c escape. */
     bool early_exit;
 
-    builtin_printf_state_t(io_streams_t &s) : streams(s), exit_code(0), early_exit(false)
+    explicit builtin_printf_state_t(io_streams_t &s) : streams(s), exit_code(0), early_exit(false)
     {
     }
 
diff --git a/src/builtin_test.cpp b/src/builtin_test.cpp
index e80d06ec0..00fb88601 100644
--- a/src/builtin_test.cpp
+++ b/src/builtin_test.cpp
@@ -173,7 +173,7 @@ private:
     }
 
 public:
-    test_parser(const wcstring_list_t &val) : strings(val)
+    explicit test_parser(const wcstring_list_t &val) : strings(val)
     { }
 
     expression *parse_expression(unsigned int start, unsigned int end);
diff --git a/src/common.h b/src/common.h
index ff7443e58..660bc0124 100644
--- a/src/common.h
+++ b/src/common.h
@@ -357,7 +357,7 @@ struct string_fuzzy_match_t
     size_t match_distance_second;
 
     /* Constructor */
-    string_fuzzy_match_t(enum fuzzy_match_type_t t, size_t distance_first = 0, size_t distance_second = 0);
+    explicit string_fuzzy_match_t(enum fuzzy_match_type_t t, size_t distance_first = 0, size_t distance_second = 0);
 
     /* Return -1, 0, 1 if this match is (respectively) better than, equal to, or worse than rhs */
     int compare(const string_fuzzy_match_t &rhs) const;
@@ -486,7 +486,7 @@ class null_terminated_array_t
 
 public:
     null_terminated_array_t() : array(NULL) { }
-    null_terminated_array_t(const string_list_t &argv) : array(make_null_terminated_array(argv))
+    explicit null_terminated_array_t(const string_list_t &argv) : array(make_null_terminated_array(argv))
     {
     }
 
@@ -576,8 +576,8 @@ class scoped_lock
 public:
     void lock(void);
     void unlock(void);
-    scoped_lock(pthread_mutex_t &mutex);
-    scoped_lock(mutex_lock_t &lock);
+    explicit scoped_lock(pthread_mutex_t &mutex);
+    explicit scoped_lock(mutex_lock_t &lock);
     ~scoped_lock();
 };
 
@@ -607,7 +607,7 @@ class scoped_rwlock
 
     /* No copying */
     scoped_rwlock &operator=(const scoped_lock &);
-    scoped_rwlock(const scoped_lock &);
+    explicit scoped_rwlock(const scoped_lock &);
 
 public:
     void lock(void);
@@ -619,8 +619,8 @@ class scoped_rwlock
        equivalent to `lock.unlock_shared(); lock.lock();`
      */
     void upgrade(void);
-    scoped_rwlock(pthread_rwlock_t &rwlock, bool shared = false);
-    scoped_rwlock(rwlock_t &rwlock, bool shared = false);
+    explicit scoped_rwlock(pthread_rwlock_t &rwlock, bool shared = false);
+    explicit scoped_rwlock(rwlock_t &rwlock, bool shared = false);
     ~scoped_rwlock();
 };
 
@@ -639,7 +639,7 @@ class scoped_push
     bool restored;
 
 public:
-    scoped_push(T *r): ref(r), saved_value(*r), restored(false)
+    explicit scoped_push(T *r): ref(r), saved_value(*r), restored(false)
     {
     }
 
diff --git a/src/complete.h b/src/complete.h
index f46370abb..6cbb13bc2 100644
--- a/src/complete.h
+++ b/src/complete.h
@@ -111,7 +111,7 @@ class completion_t
     complete_flags_t flags;
 
     /* Construction. Note: defining these so that they are not inlined reduces the executable size. */
-    completion_t(const wcstring &comp, const wcstring &desc = wcstring(), string_fuzzy_match_t match = string_fuzzy_match_t(fuzzy_match_exact), complete_flags_t flags_val = 0);
+    explicit completion_t(const wcstring &comp, const wcstring &desc = wcstring(), string_fuzzy_match_t match = string_fuzzy_match_t(fuzzy_match_exact), complete_flags_t flags_val = 0);
     completion_t(const completion_t &);
     completion_t &operator=(const completion_t &);
 
diff --git a/src/env.h b/src/env.h
index bfea16aba..3eb6313f9 100644
--- a/src/env.h
+++ b/src/env.h
@@ -101,12 +101,11 @@ class env_var_t : public wcstring
 private:
     bool is_missing;
 public:
-    static env_var_t missing_var(void)
+    static env_var_t missing_var()
     {
-        env_var_t result(L"");
+        env_var_t result((wcstring()));
         result.is_missing = true;
         return result;
-
     }
 
     env_var_t(const env_var_t &x) : wcstring(x), is_missing(x.is_missing) { }
diff --git a/src/env_universal_common.cpp b/src/env_universal_common.cpp
index bb1815048..f7c07ea28 100644
--- a/src/env_universal_common.cpp
+++ b/src/env_universal_common.cpp
@@ -338,7 +338,7 @@ env_var_t env_universal_t::get(const wcstring &name) const
     var_table_t::const_iterator where = vars.find(name);
     if (where != vars.end())
     {
-        result = where->second.val;
+        result = env_var_t(where->second.val);
     }
     return result;
 }
@@ -1454,7 +1454,7 @@ class universal_notifier_named_pipe_t : public universal_notifier_t
     }
     
     public:
-    universal_notifier_named_pipe_t(const wchar_t *test_path) : pipe_fd(-1), readback_time_usec(0), readback_amount(0), polling_due_to_readable_fd(false), drain_if_still_readable_time_usec(0)
+    explicit universal_notifier_named_pipe_t(const wchar_t *test_path) : pipe_fd(-1), readback_time_usec(0), readback_amount(0), polling_due_to_readable_fd(false), drain_if_still_readable_time_usec(0)
     {
         make_pipe(test_path);
     }
diff --git a/src/env_universal_common.h b/src/env_universal_common.h
index 3428c6937..60cf00278 100644
--- a/src/env_universal_common.h
+++ b/src/env_universal_common.h
@@ -75,7 +75,7 @@ class env_universal_t
     static var_table_t read_message_internal(int fd);
     
 public:
-    env_universal_t(const wcstring &path);
+    explicit env_universal_t(const wcstring &path);
     ~env_universal_t();
     
     /* Get the value of the variable with the specified name */
diff --git a/src/event.h b/src/event.h
index 80737596d..bf068c5d3 100644
--- a/src/event.h
+++ b/src/event.h
@@ -87,7 +87,7 @@ struct event_t
     */
     wcstring_list_t arguments;
 
-    event_t(int t);
+    explicit event_t(int t);
     ~event_t();
 
     static event_t signal_event(int sig);
diff --git a/src/fish_tests.cpp b/src/fish_tests.cpp
index adbc13a53..efc134d73 100644
--- a/src/fish_tests.cpp
+++ b/src/fish_tests.cpp
@@ -1318,7 +1318,7 @@ static void test_escape_sequences(void)
 class lru_node_test_t : public lru_node_t
 {
 public:
-    lru_node_test_t(const wcstring &tmp) : lru_node_t(tmp) { }
+    explicit lru_node_test_t(const wcstring &tmp) : lru_node_t(tmp) { }
 };
 
 class test_lru_t : public lru_cache_t<lru_node_test_t>
diff --git a/src/history.cpp b/src/history.cpp
index 112af1eaf..28be7bc55 100644
--- a/src/history.cpp
+++ b/src/history.cpp
@@ -129,7 +129,7 @@ class time_profiler_t
     double start;
 public:
 
-    time_profiler_t(const char *w)
+    explicit time_profiler_t(const char *w)
     {
         if (LOG_TIMES)
         {
@@ -165,7 +165,7 @@ class history_lru_node_t : public lru_node_t
 public:
     time_t timestamp;
     path_list_t required_paths;
-    history_lru_node_t(const history_item_t &item) :
+    explicit history_lru_node_t(const history_item_t &item) :
         lru_node_t(item.str()),
         timestamp(item.timestamp()),
         required_paths(item.required_paths)
@@ -183,7 +183,7 @@ protected:
     }
 
 public:
-    history_lru_cache_t(size_t max) : lru_cache_t<history_lru_node_t>(max) { }
+    explicit history_lru_cache_t(size_t max) : lru_cache_t<history_lru_node_t>(max) { }
 
     /* Function to add a history item */
     void add_item(const history_item_t &item)
diff --git a/src/history.h b/src/history.h
index 63372ba02..f99950aa0 100644
--- a/src/history.h
+++ b/src/history.h
@@ -116,7 +116,7 @@ class history_t
     history_t &operator=(const history_t&);
 
     /** Private creator */
-    history_t(const wcstring &pname);
+    explicit history_t(const wcstring &pname);
 
     /** Privately add an item. If pending, the item will not be returned by history searches until a call to resolve_pending. */
     void add(const history_item_t &item, bool pending = false);
@@ -348,7 +348,7 @@ void history_sanity_check();
 struct file_detection_context_t
 {
     /* Constructor */
-    file_detection_context_t(history_t *hist, history_identifier_t ident = 0);
+    explicit file_detection_context_t(history_t *hist, history_identifier_t ident = 0);
 
     /* Determine which of potential_paths are valid, and put them in valid_paths */
     int perform_file_detection();
diff --git a/src/io.h b/src/io.h
index bb4c0621d..adc59be17 100644
--- a/src/io.h
+++ b/src/io.h
@@ -56,7 +56,7 @@ class io_data_t
 class io_close_t : public io_data_t
 {
 public:
-    io_close_t(int f) :
+    explicit io_close_t(int f) :
         io_data_t(IO_CLOSE, f)
     {
     }
@@ -137,7 +137,7 @@ class io_buffer_t : public io_pipe_t
     /** buffer to save output in */
     std::vector<char> out_buffer;
 
-    io_buffer_t(int f):
+    explicit io_buffer_t(int f):
         io_pipe_t(IO_BUFFER, f, false /* not input */),
         out_buffer()
     {
@@ -195,7 +195,7 @@ class io_chain_t : public std::vector<shared_ptr<io_data_t> >
 {
 public:
     io_chain_t();
-    io_chain_t(const shared_ptr<io_data_t> &);
+    explicit 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);
diff --git a/src/lru.h b/src/lru.h
index 779c2edcf..a70b165d6 100644
--- a/src/lru.h
+++ b/src/lru.h
@@ -35,7 +35,7 @@ class lru_node_t
     const wcstring key;
 
     /** Constructor */
-    lru_node_t(const wcstring &pkey) : prev(NULL), next(NULL), key(pkey) { }
+    explicit lru_node_t(const wcstring &pkey) : prev(NULL), next(NULL), key(pkey) { }
 
     /** Virtual destructor that does nothing for classes that inherit lru_node_t */
     virtual ~lru_node_t() {}
@@ -117,7 +117,7 @@ class lru_cache_t
 public:
 
     /** Constructor */
-    lru_cache_t(size_t max_size = 1024) : max_node_count(max_size), node_count(0), mouth(wcstring())
+    explicit lru_cache_t(size_t max_size = 1024) : max_node_count(max_size), node_count(0), mouth(wcstring())
     {
         /* Hook up the mouth to itself: a one node circularly linked list! */
         mouth.prev = mouth.next = &mouth;
@@ -220,7 +220,7 @@ class lru_cache_t
     {
         lru_node_t *node;
     public:
-        iterator(lru_node_t *val) : node(val) { }
+        explicit iterator(lru_node_t *val) : node(val) { }
         void operator++()
         {
             node = lru_cache_t::get_previous(node);
diff --git a/src/parse_tree.cpp b/src/parse_tree.cpp
index ead78a6e5..5939e270d 100644
--- a/src/parse_tree.cpp
+++ b/src/parse_tree.cpp
@@ -628,7 +628,7 @@ class parse_ll_t
 public:
 
     /* Constructor */
-    parse_ll_t(enum parse_token_type_t goal) : fatal_errored(false), should_generate_error_messages(true)
+    explicit parse_ll_t(enum parse_token_type_t goal) : fatal_errored(false), should_generate_error_messages(true)
     {
         this->symbol_stack.reserve(16);
         this->nodes.reserve(64);
diff --git a/src/parser.h b/src/parser.h
index 1b2bad1b5..db35471be 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -85,7 +85,7 @@ struct block_t
 {
 protected:
     /** Protected constructor. Use one of the subclasses below. */
-    block_t(block_type_t t);
+    explicit block_t(block_type_t t);
 
 private:
     const block_type_t block_type; /**< Type of block. */
@@ -134,7 +134,7 @@ struct if_block_t : public block_t
 struct event_block_t : public block_t
 {
     event_t const event;
-    event_block_t(const event_t &evt);
+    explicit event_block_t(const event_t &evt);
 };
 
 struct function_block_t : public block_t
@@ -147,7 +147,7 @@ struct function_block_t : public block_t
 struct source_block_t : public block_t
 {
     const wchar_t * const source_file;
-    source_block_t(const wchar_t *src);
+    explicit source_block_t(const wchar_t *src);
 };
 
 struct for_block_t : public block_t
@@ -172,7 +172,7 @@ struct fake_block_t : public block_t
 
 struct scope_block_t : public block_t
 {
-    scope_block_t(block_type_t type); //must be BEGIN, TOP or SUBST
+    explicit scope_block_t(block_type_t type); //must be BEGIN, TOP or SUBST
 };
 
 struct breakpoint_block_t : public block_t
diff --git a/src/proc.cpp b/src/proc.cpp
index 0a0da0a8b..e16688f02 100644
--- a/src/proc.cpp
+++ b/src/proc.cpp
@@ -354,8 +354,6 @@ int job_signal(job_t *j, int signal)
 
 /**
    Store the status of the process pid that was returned by waitpid.
-   Return 0 if all went well, nonzero otherwise.
-   This is called from a signal handler.
 */
 static void mark_process_status(const job_t *j, process_t *p, int status)
 {
@@ -374,18 +372,7 @@ static void mark_process_status(const job_t *j, process_t *p, int status)
     {
         /* This should never be reached */
         p->completed = 1;
-
-        char mess[MESS_SIZE];
-        snprintf(mess,
-                 MESS_SIZE,
-                 "Process %ld exited abnormally\n",
-                 (long) p->pid);
-        /*
-          If write fails, do nothing. We're in a signal handlers error
-          handler. If things aren't working properly, it's safer to
-          give up.
-         */
-        write_ignore(2, mess, strlen(mess));
+        fprintf(stderr, "Process %ld exited abnormally\n", (long)p->pid);
     }
 }
 
@@ -399,10 +386,8 @@ void job_mark_process_as_failed(const job_t *job, process_t *p)
 }
 
 /**
-   Handle status update for child \c pid. This function is called by
-   the signal handler, so it mustn't use malloc or any such hitech
-   nonsense.
-
+   Handle status update for child \c pid.
+ 
    \param pid the pid of the process whose status changes
    \param status the status as returned by wait
 */
@@ -411,14 +396,6 @@ static void handle_child_status(pid_t pid, int status)
     bool found_proc = false;
     const job_t *j = NULL;
     process_t *p = NULL;
-//	char mess[MESS_SIZE];
-    /*
-      snprintf( mess,
-      MESS_SIZE,
-      "Process %d\n",
-      (int) pid );
-      write( 2, mess, strlen(mess ));
-    */
 
     job_iterator_t jobs;
     while (! found_proc && (j = jobs.next()))
diff --git a/src/proc.h b/src/proc.h
index 8dd66c7ce..68ec54543 100644
--- a/src/proc.h
+++ b/src/proc.h
@@ -422,7 +422,7 @@ class job_iterator_t
         return job;
     }
 
-    job_iterator_t(job_list_t &jobs);
+    explicit job_iterator_t(job_list_t &jobs);
     job_iterator_t();
     size_t count() const;
 };
diff --git a/src/screen.cpp b/src/screen.cpp
index dc78d2278..7bb5cf4bd 100644
--- a/src/screen.cpp
+++ b/src/screen.cpp
@@ -74,7 +74,7 @@ class scoped_buffer_t
     int (* const old_writer)(char);
 
 public:
-    scoped_buffer_t(data_buffer_t *buff) : old_buff(s_writeb_buffer), old_writer(output_get_writer())
+    explicit scoped_buffer_t(data_buffer_t *buff) : old_buff(s_writeb_buffer), old_writer(output_get_writer())
     {
         s_writeb_buffer = buff;
         output_set_writer(s_writeb);
diff --git a/src/tokenizer.h b/src/tokenizer.h
index d88feef6c..d6de25598 100644
--- a/src/tokenizer.h
+++ b/src/tokenizer.h
@@ -195,7 +195,7 @@ class move_word_state_machine_t
 
 public:
 
-    move_word_state_machine_t(move_word_style_t st);
+    explicit move_word_state_machine_t(move_word_style_t st);
     bool consume_char(wchar_t c);
     void reset();
 };