diff --git a/src/app/config/config.c b/src/app/config/config.c
index 90eae50fdd..e33c6b26e8 100644
--- a/src/app/config/config.c
+++ b/src/app/config/config.c
@@ -142,7 +142,7 @@
 #include "lib/process/pidfile.h"
 #include "lib/process/restrict.h"
 #include "lib/process/setuid.h"
-#include "lib/process/subprocess.h"
+#include "lib/process/process.h"
 #include "lib/net/gethostname.h"
 #include "lib/thread/numcpus.h"
 
diff --git a/src/feature/client/transports.c b/src/feature/client/transports.c
index fd4bec7807..0e326f90e9 100644
--- a/src/feature/client/transports.c
+++ b/src/feature/client/transports.c
@@ -103,7 +103,6 @@
 #include "feature/control/control.h"
 
 #include "lib/process/process.h"
-#include "lib/process/subprocess.h"
 #include "lib/process/env.h"
 
 static smartlist_t *
diff --git a/src/lib/process/include.am b/src/lib/process/include.am
index aa73356146..a2d54b6238 100644
--- a/src/lib/process/include.am
+++ b/src/lib/process/include.am
@@ -14,7 +14,6 @@ src_lib_libtor_process_a_SOURCES =		\
 	src/lib/process/process_win32.c		\
 	src/lib/process/restrict.c		\
 	src/lib/process/setuid.c		\
-	src/lib/process/subprocess.c		\
 	src/lib/process/waitpid.c		\
 	src/lib/process/winprocess_sys.c
 
@@ -32,6 +31,5 @@ noinst_HEADERS +=				\
 	src/lib/process/process_win32.h		\
 	src/lib/process/restrict.h		\
 	src/lib/process/setuid.h		\
-	src/lib/process/subprocess.h		\
 	src/lib/process/waitpid.h		\
 	src/lib/process/winprocess_sys.h
diff --git a/src/lib/process/process.c b/src/lib/process/process.c
index 915217e132..7275d0a21b 100644
--- a/src/lib/process/process.c
+++ b/src/lib/process/process.c
@@ -26,6 +26,12 @@
 /** A list of all <b>process_t</b> instances currently allocated. */
 static smartlist_t *processes;
 
+/**
+ * Boolean.  If true, then Tor may call execve or CreateProcess via
+ * tor_spawn_background.
+ **/
+static int may_spawn_background_process = 1;
+
 /** Structure to represent a child process. */
 struct process_t {
   /** Process status. */
@@ -114,6 +120,16 @@ process_protocol_to_string(process_protocol_t protocol)
   /* LCOV_EXCL_STOP */
 }
 
+/**
+ * Turn off may_spawn_background_process, so that all future calls to
+ * tor_spawn_background are guaranteed to fail.
+ **/
+void
+tor_disable_spawning_background_processes(void)
+{
+  may_spawn_background_process = 0;
+}
+
 /** Initialize the Process subsystem.  This function initializes the Process
  * subsystem's global state. For cleaning up, <b>process_free_all()</b> should
  * be called. */
@@ -234,6 +250,9 @@ process_exec(process_t *process)
 {
   tor_assert(process);
 
+  if (BUG(may_spawn_background_process == 0))
+    return PROCESS_STATUS_ERROR;
+
   process_status_t status = PROCESS_STATUS_NOT_RUNNING;
 
   log_info(LD_PROCESS, "Starting new process: %s", process->command);
diff --git a/src/lib/process/process.h b/src/lib/process/process.h
index 6092c2da7d..cb5bccbf7b 100644
--- a/src/lib/process/process.h
+++ b/src/lib/process/process.h
@@ -45,6 +45,8 @@ typedef enum {
 
 const char *process_protocol_to_string(process_protocol_t protocol);
 
+void tor_disable_spawning_background_processes(void);
+
 struct process_t;
 typedef struct process_t process_t;
 
diff --git a/src/lib/process/process_win32.c b/src/lib/process/process_win32.c
index 7b18903c70..73e19d518f 100644
--- a/src/lib/process/process_win32.c
+++ b/src/lib/process/process_win32.c
@@ -18,13 +18,16 @@
 #include "lib/log/win32err.h"
 #include "lib/process/process.h"
 #include "lib/process/process_win32.h"
-#include "lib/process/subprocess.h"
 #include "lib/process/env.h"
 
 #ifdef HAVE_SYS_TIME_H
 #include <sys/time.h>
 #endif
 
+#ifdef HAVE_STRING_H
+#include <string.h>
+#endif
+
 #ifdef _WIN32
 
 /** The size of our intermediate buffers. */
@@ -889,4 +892,104 @@ process_win32_handle_read_completion(process_win32_handle_t *handle,
   return false;
 }
 
+/** Format a single argument for being put on a Windows command line.
+ * Returns a newly allocated string */
+STATIC char *
+format_win_cmdline_argument(const char *arg)
+{
+  char *formatted_arg;
+  char need_quotes;
+  const char *c;
+  int i;
+  int bs_counter = 0;
+  /* Backslash we can point to when one is inserted into the string */
+  const char backslash = '\\';
+
+  /* Smartlist of *char */
+  smartlist_t *arg_chars;
+  arg_chars = smartlist_new();
+
+  /* Quote string if it contains whitespace or is empty */
+  need_quotes = (strchr(arg, ' ') || strchr(arg, '\t') || '\0' == arg[0]);
+
+  /* Build up smartlist of *chars */
+  for (c=arg; *c != '\0'; c++) {
+    if ('"' == *c) {
+      /* Double up backslashes preceding a quote */
+      for (i=0; i<(bs_counter*2); i++)
+        smartlist_add(arg_chars, (void*)&backslash);
+      bs_counter = 0;
+      /* Escape the quote */
+      smartlist_add(arg_chars, (void*)&backslash);
+      smartlist_add(arg_chars, (void*)c);
+    } else if ('\\' == *c) {
+      /* Count backslashes until we know whether to double up */
+      bs_counter++;
+    } else {
+      /* Don't double up slashes preceding a non-quote */
+      for (i=0; i<bs_counter; i++)
+        smartlist_add(arg_chars, (void*)&backslash);
+      bs_counter = 0;
+      smartlist_add(arg_chars, (void*)c);
+    }
+  }
+  /* Don't double up trailing backslashes */
+  for (i=0; i<bs_counter; i++)
+    smartlist_add(arg_chars, (void*)&backslash);
+
+  /* Allocate space for argument, quotes (if needed), and terminator */
+  const size_t formatted_arg_len = smartlist_len(arg_chars) +
+    (need_quotes ? 2 : 0) + 1;
+  formatted_arg = tor_malloc_zero(formatted_arg_len);
+
+  /* Add leading quote */
+  i=0;
+  if (need_quotes)
+    formatted_arg[i++] = '"';
+
+  /* Add characters */
+  SMARTLIST_FOREACH(arg_chars, char*, ch,
+  {
+    formatted_arg[i++] = *ch;
+  });
+
+  /* Add trailing quote */
+  if (need_quotes)
+    formatted_arg[i++] = '"';
+  formatted_arg[i] = '\0';
+
+  smartlist_free(arg_chars);
+  return formatted_arg;
+}
+
+/** Format a command line for use on Windows, which takes the command as a
+ * string rather than string array. Follows the rules from "Parsing C++
+ * Command-Line Arguments" in MSDN. Algorithm based on list2cmdline in the
+ * Python subprocess module. Returns a newly allocated string */
+STATIC char *
+tor_join_win_cmdline(const char *argv[])
+{
+  smartlist_t *argv_list;
+  char *joined_argv;
+  int i;
+
+  /* Format each argument and put the result in a smartlist */
+  argv_list = smartlist_new();
+  for (i=0; argv[i] != NULL; i++) {
+    smartlist_add(argv_list, (void *)format_win_cmdline_argument(argv[i]));
+  }
+
+  /* Join the arguments with whitespace */
+  joined_argv = smartlist_join_strings(argv_list, " ", 0, NULL);
+
+  /* Free the newly allocated arguments, and the smartlist */
+  SMARTLIST_FOREACH(argv_list, char *, arg,
+  {
+    tor_free(arg);
+  });
+  smartlist_free(argv_list);
+
+  return joined_argv;
+}
+
 #endif /* ! defined(_WIN32). */
diff --git a/src/lib/process/process_win32.h b/src/lib/process/process_win32.h
index 9a42e6c713..3c809dfd23 100644
--- a/src/lib/process/process_win32.h
+++ b/src/lib/process/process_win32.h
@@ -86,6 +86,9 @@ STATIC int process_win32_read_from_handle(process_win32_handle_t *,
 STATIC bool process_win32_handle_read_completion(process_win32_handle_t *,
                                                  DWORD,
                                                  DWORD);
+
+STATIC char *format_win_cmdline_argument(const char *arg);
+STATIC char *tor_join_win_cmdline(const char *argv[]);
 #endif /* defined(PROCESS_WIN32_PRIVATE). */
 
 #endif /* ! defined(_WIN32). */
diff --git a/src/lib/process/subprocess.c b/src/lib/process/subprocess.c
deleted file mode 100644
index c163790155..0000000000
--- a/src/lib/process/subprocess.c
+++ /dev/null
@@ -1,158 +0,0 @@
-/* Copyright (c) 2003, Roger Dingledine
- * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
- * Copyright (c) 2007-2018, The Tor Project, Inc. */
-/* See LICENSE for licensing information */
-
-/**
- * \file subprocess.c
- * \brief Launch and monitor other processes.
- **/
-
-#define SUBPROCESS_PRIVATE
-#include "lib/process/subprocess.h"
-
-#include "lib/container/smartlist.h"
-#include "lib/err/torerr.h"
-#include "lib/log/log.h"
-#include "lib/log/util_bug.h"
-#include "lib/log/win32err.h"
-#include "lib/malloc/malloc.h"
-#include "lib/process/env.h"
-#include "lib/process/waitpid.h"
-#include "lib/string/compat_ctype.h"
-
-#ifdef HAVE_SYS_TYPES_H
-#include <sys/types.h>
-#endif
-#ifdef HAVE_SYS_PRCTL_H
-#include <sys/prctl.h>
-#endif
-#ifdef HAVE_UNISTD_H
-#include <unistd.h>
-#endif
-#ifdef HAVE_SIGNAL_H
-#include <signal.h>
-#endif
-#ifdef HAVE_FCNTL_H
-#include <fcntl.h>
-#endif
-#ifdef HAVE_SYS_WAIT_H
-#include <sys/wait.h>
-#endif
-#include <errno.h>
-#include <string.h>
-
-/** Format a single argument for being put on a Windows command line.
- * Returns a newly allocated string */
-static char *
-format_win_cmdline_argument(const char *arg)
-{
-  char *formatted_arg;
-  char need_quotes;
-  const char *c;
-  int i;
-  int bs_counter = 0;
-  /* Backslash we can point to when one is inserted into the string */
-  const char backslash = '\\';
-
-  /* Smartlist of *char */
-  smartlist_t *arg_chars;
-  arg_chars = smartlist_new();
-
-  /* Quote string if it contains whitespace or is empty */
-  need_quotes = (strchr(arg, ' ') || strchr(arg, '\t') || '\0' == arg[0]);
-
-  /* Build up smartlist of *chars */
-  for (c=arg; *c != '\0'; c++) {
-    if ('"' == *c) {
-      /* Double up backslashes preceding a quote */
-      for (i=0; i<(bs_counter*2); i++)
-        smartlist_add(arg_chars, (void*)&backslash);
-      bs_counter = 0;
-      /* Escape the quote */
-      smartlist_add(arg_chars, (void*)&backslash);
-      smartlist_add(arg_chars, (void*)c);
-    } else if ('\\' == *c) {
-      /* Count backslashes until we know whether to double up */
-      bs_counter++;
-    } else {
-      /* Don't double up slashes preceding a non-quote */
-      for (i=0; i<bs_counter; i++)
-        smartlist_add(arg_chars, (void*)&backslash);
-      bs_counter = 0;
-      smartlist_add(arg_chars, (void*)c);
-    }
-  }
-  /* Don't double up trailing backslashes */
-  for (i=0; i<bs_counter; i++)
-    smartlist_add(arg_chars, (void*)&backslash);
-
-  /* Allocate space for argument, quotes (if needed), and terminator */
-  const size_t formatted_arg_len = smartlist_len(arg_chars) +
-    (need_quotes ? 2 : 0) + 1;
-  formatted_arg = tor_malloc_zero(formatted_arg_len);
-
-  /* Add leading quote */
-  i=0;
-  if (need_quotes)
-    formatted_arg[i++] = '"';
-
-  /* Add characters */
-  SMARTLIST_FOREACH(arg_chars, char*, ch,
-  {
-    formatted_arg[i++] = *ch;
-  });
-
-  /* Add trailing quote */
-  if (need_quotes)
-    formatted_arg[i++] = '"';
-  formatted_arg[i] = '\0';
-
-  smartlist_free(arg_chars);
-  return formatted_arg;
-}
-
-/** Format a command line for use on Windows, which takes the command as a
- * string rather than string array. Follows the rules from "Parsing C++
- * Command-Line Arguments" in MSDN. Algorithm based on list2cmdline in the
- * Python subprocess module. Returns a newly allocated string */
-char *
-tor_join_win_cmdline(const char *argv[])
-{
-  smartlist_t *argv_list;
-  char *joined_argv;
-  int i;
-
-  /* Format each argument and put the result in a smartlist */
-  argv_list = smartlist_new();
-  for (i=0; argv[i] != NULL; i++) {
-    smartlist_add(argv_list, (void *)format_win_cmdline_argument(argv[i]));
-  }
-
-  /* Join the arguments with whitespace */
-  joined_argv = smartlist_join_strings(argv_list, " ", 0, NULL);
-
-  /* Free the newly allocated arguments, and the smartlist */
-  SMARTLIST_FOREACH(argv_list, char *, arg,
-  {
-    tor_free(arg);
-  });
-  smartlist_free(argv_list);
-
-  return joined_argv;
-}
-
-/**
- * Boolean.  If true, then Tor may call execve or CreateProcess via
- * tor_spawn_background.
- **/
-static int may_spawn_background_process = 1;
-/**
- * Turn off may_spawn_background_process, so that all future calls to
- * tor_spawn_background are guaranteed to fail.
- **/
-void
-tor_disable_spawning_background_processes(void)
-{
-  may_spawn_background_process = 0;
-}
diff --git a/src/lib/process/subprocess.h b/src/lib/process/subprocess.h
deleted file mode 100644
index eb91626343..0000000000
--- a/src/lib/process/subprocess.h
+++ /dev/null
@@ -1,20 +0,0 @@
-/* Copyright (c) 2003-2004, Roger Dingledine
- * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
- * Copyright (c) 2007-2018, The Tor Project, Inc. */
-/* See LICENSE for licensing information */
-
-/**
- * \file subprocess.h
- * \brief Header for subprocess.c
- **/
-
-#ifndef TOR_SUBPROCESS_H
-#define TOR_SUBPROCESS_H
-
-void tor_disable_spawning_background_processes(void);
-
-#ifndef _WIN32
-char *tor_join_win_cmdline(const char *argv[]);
-#endif
-
-#endif
diff --git a/src/test/test_logging.c b/src/test/test_logging.c
index 9d3ee5d55f..2ecae461a3 100644
--- a/src/test/test_logging.c
+++ b/src/test/test_logging.c
@@ -9,7 +9,6 @@
 #include "lib/err/torerr.h"
 #include "lib/log/log.h"
 #include "test/test.h"
-#include "lib/process/subprocess.h"
 
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
diff --git a/src/test/test_process.c b/src/test/test_process.c
index 2fcb3f6686..3640b86688 100644
--- a/src/test/test_process.c
+++ b/src/test/test_process.c
@@ -628,11 +628,51 @@ test_win32(void *arg)
   process_init();
 
   process_t *process = process_new("");
+  char *joined_argv = NULL;
 
   /* On Win32 all processes should have a Win32 process handle. */
   tt_ptr_op(NULL, OP_NE, process_get_win32_process(process));
 
+  /* Based on some test cases from "Parsing C++ Command-Line Arguments" in
+   * MSDN but we don't exercise all quoting rules because tor_join_win_cmdline
+   * will try to only generate simple cases for the child process to parse;
+   * i.e. we never embed quoted strings in arguments. */
+
+  const char *argvs[][4] = {
+    {"a", "bb", "CCC", NULL}, // Normal
+    {NULL, NULL, NULL, NULL}, // Empty argument list
+    {"", NULL, NULL, NULL}, // Empty argument
+    {"\"a", "b\"b", "CCC\"", NULL}, // Quotes
+    {"a\tbc", "dd  dd", "E", NULL}, // Whitespace
+    {"a\\\\\\b", "de fg", "H", NULL}, // Backslashes
+    {"a\\\"b", "\\c", "D\\", NULL}, // Backslashes before quote
+    {"a\\\\b c", "d", "E", NULL}, // Backslashes not before quote
+    { NULL } // Terminator
+  };
+
+  const char *cmdlines[] = {
+    "a bb CCC",
+    "",
+    "\"\"",
+    "\\\"a b\\\"b CCC\\\"",
+    "\"a\tbc\" \"dd  dd\" E",
+    "a\\\\\\b \"de fg\" H",
+    "a\\\\\\\"b \\c D\\",
+    "\"a\\\\b c\" d E",
+    NULL // Terminator
+  };
+
+  int i;
+
+  for (i=0; cmdlines[i]!=NULL; i++) {
+    log_info(LD_GENERAL, "Joining argvs[%d], expecting <%s>", i, cmdlines[i]);
+    joined_argv = tor_join_win_cmdline(argvs[i]);
+    tt_str_op(cmdlines[i],OP_EQ, joined_argv);
+    tor_free(joined_argv);
+  }
+
  done:
+  tor_free(joined_argv);
   process_free(process);
   process_free_all();
 #endif
diff --git a/src/test/test_pt.c b/src/test/test_pt.c
index c980276b14..b5572ef80c 100644
--- a/src/test/test_pt.c
+++ b/src/test/test_pt.c
@@ -8,7 +8,6 @@
 #define UTIL_PRIVATE
 #define STATEFILE_PRIVATE
 #define CONTROL_PRIVATE
-#define SUBPROCESS_PRIVATE
 #define PROCESS_PRIVATE
 #include "core/or/or.h"
 #include "app/config/config.h"
@@ -18,7 +17,6 @@
 #include "core/or/circuitbuild.h"
 #include "app/config/statefile.h"
 #include "test/test.h"
-#include "lib/process/subprocess.h"
 #include "lib/encoding/confline.h"
 #include "lib/net/resolve.h"
 #include "lib/process/process.h"
diff --git a/src/test/test_util.c b/src/test/test_util.c
index 4fa67b6419..a94153f2dc 100644
--- a/src/test/test_util.c
+++ b/src/test/test_util.c
@@ -10,7 +10,7 @@
 #define UTIL_PRIVATE
 #define UTIL_MALLOC_PRIVATE
 #define SOCKET_PRIVATE
-#define SUBPROCESS_PRIVATE
+#define PROCESS_WIN32_PRIVATE
 #include "lib/testsupport/testsupport.h"
 #include "core/or/or.h"
 #include "lib/container/buffers.h"
@@ -22,6 +22,7 @@
 #include "test/test.h"
 #include "lib/memarea/memarea.h"
 #include "lib/process/waitpid.h"
+#include "lib/process/process_win32.h"
 #include "test/log_test_helpers.h"
 #include "lib/compress/compress.h"
 #include "lib/compress/compress_zstd.h"
@@ -30,7 +31,6 @@
 #include "lib/fs/winlib.h"
 #include "lib/process/env.h"
 #include "lib/process/pidfile.h"
-#include "lib/process/subprocess.h"
 #include "lib/intmath/weakrng.h"
 #include "lib/thread/numcpus.h"
 #include "lib/math/fp.h"
@@ -4395,57 +4395,6 @@ test_util_format_dec_number(void *ptr)
   return;
 }
 
-/**
- * Test that we can properly format a Windows command line
- */
-static void
-test_util_join_win_cmdline(void *ptr)
-{
-  /* Based on some test cases from "Parsing C++ Command-Line Arguments" in
-   * MSDN but we don't exercise all quoting rules because tor_join_win_cmdline
-   * will try to only generate simple cases for the child process to parse;
-   * i.e. we never embed quoted strings in arguments. */
-
-  const char *argvs[][4] = {
-    {"a", "bb", "CCC", NULL}, // Normal
-    {NULL, NULL, NULL, NULL}, // Empty argument list
-    {"", NULL, NULL, NULL}, // Empty argument
-    {"\"a", "b\"b", "CCC\"", NULL}, // Quotes
-    {"a\tbc", "dd  dd", "E", NULL}, // Whitespace
-    {"a\\\\\\b", "de fg", "H", NULL}, // Backslashes
-    {"a\\\"b", "\\c", "D\\", NULL}, // Backslashes before quote
-    {"a\\\\b c", "d", "E", NULL}, // Backslashes not before quote
-    { NULL } // Terminator
-  };
-
-  const char *cmdlines[] = {
-    "a bb CCC",
-    "",
-    "\"\"",
-    "\\\"a b\\\"b CCC\\\"",
-    "\"a\tbc\" \"dd  dd\" E",
-    "a\\\\\\b \"de fg\" H",
-    "a\\\\\\\"b \\c D\\",
-    "\"a\\\\b c\" d E",
-    NULL // Terminator
-  };
-
-  int i;
-  char *joined_argv = NULL;
-
-  (void)ptr;
-
-  for (i=0; cmdlines[i]!=NULL; i++) {
-    log_info(LD_GENERAL, "Joining argvs[%d], expecting <%s>", i, cmdlines[i]);
-    joined_argv = tor_join_win_cmdline(argvs[i]);
-    tt_str_op(cmdlines[i],OP_EQ, joined_argv);
-    tor_free(joined_argv);
-  }
-
- done:
-  tor_free(joined_argv);
-}
-
 #define MAX_SPLIT_LINE_COUNT 4
 struct split_lines_test_t {
   const char *orig_line; // Line to be split (may contain \0's)
@@ -6226,7 +6175,6 @@ struct testcase_t util_tests[] = {
   UTIL_TEST_WIN_ONLY(load_win_lib, 0),
   UTIL_TEST(format_hex_number, 0),
   UTIL_TEST(format_dec_number, 0),
-  UTIL_TEST(join_win_cmdline, 0),
   UTIL_TEST(n_bits_set, 0),
   UTIL_TEST(eat_whitespace, 0),
   UTIL_TEST(sl_new_from_text_lines, 0),