sh-quote, execute, spawn-pipe, etc.: Make better use of 'const'.

* lib/sh-quote.h (shell_quote_argv): Does not need write access to the
elements of argv.
* lib/sh-quote.c (shell_quote_argv): Likewise.
* lib/windows-spawn.h (prepare_spawn): Add 'const' the argument type and
the return type.
* lib/windows-spawn.c (prepare_spawn): Likewise.
* lib/os2-spawn.h (prepare_spawn): Likewise.
* lib/os2-spawn.c (prepare_spawn): Likewise.
* lib/execute.h (execute): Does not need write access to the elements of
prog_argv.
* lib/execute.c (execute): Likewise.
* lib/spawn-pipe.h (create_pipe_out, create_pipe_in, create_pipe_bidi):
Likewise.
* lib/spawn-pipe.c (create_pipe, create_pipe_bidi, create_pipe_in,
create_pipe_out): Likewise.
* lib/pipe-filter.h (pipe_filter_ii_execute, pipe_filter_gi_create):
Likewise.
* lib/pipe-filter-ii.c (pipe_filter_ii_execute): Likewise.
* lib/pipe-filter-gi.c (pipe_filter_gi_create): Likewise.
* lib/javaexec.h (execute_fn): Does not need write access to the
elements of prog_argv.
* lib/javaexec.c (execute_java_class): Update variable types and remove
casts to 'char *'.
* lib/csharpexec.h (execute_fn): Does not need write access to the
elements of prog_argv.
* lib/csharpexec.c (execute_csharp_using_mono,
execute_csharp_using_sscli): Update variable types and remove casts to
'char *'.
* lib/javacomp.c (compile_using_envjavac, compile_using_gcj,
compile_using_javac, compile_using_jikes, is_envjavac_gcj,
is_envjavac_gcj43, is_gcj_present, is_gcj_43, is_javac_present,
is_jikes_present): Update variable types and remove casts to 'char *'.
* lib/javaversion.c (execute_and_read_line): Does not need write access
to the elements of prog_argv.
* lib/csharpcomp.c (compile_csharp_using_mono,
compile_csharp_using_sscli): Update variable types and remove casts to
'char *'.
* tests/test-sh-quote.c (main): Update variable types and remove casts
to 'char *'.
* tests/test-execute-main.c (main): Update variable types and remove
casts to 'char *'.
* tests/test-spawn-pipe-main.c (test_pipe): Update variable types and
remove casts to 'char *'.
* NEWS: Mention the changes.

20 files changed, 145 insertions, 131 deletions

diff --git a/lib/csharpcomp.c b/lib/csharpcomp.c
index 57d2084b0a..cf4e2a50c5 100644
--- a/lib/csharpcomp.c
+++ b/lib/csharpcomp.c
@@ -76,7 +76,7 @@ compile_csharp_using_mono (const char * const *sources,
          "mcs --version >/dev/null 2>/dev/null"
          and (to exclude an unrelated 'mcs' program on QNX 6)
          "mcs --version 2>/dev/null | grep Mono >/dev/null"  */
-      char *argv[3];
+      const char *argv[3];
       pid_t child;
       int fd[1];
       int exitstatus;
@@ -121,8 +121,8 @@ compile_csharp_using_mono (const char * const *sources,
   if (mcs_present)
     {
       unsigned int argc;
-      char **argv;
-      char **argp;
+      const char **argv;
+      const char **argp;
       pid_t child;
       int fd[1];
       FILE *fp;
@@ -136,7 +136,7 @@ compile_csharp_using_mono (const char * const *sources,
       argc =
         1 + (output_is_library ? 1 : 0) + 1 + libdirs_count + libraries_count
         + (debug ? 1 : 0) + sources_count;
-      argv = (char **) xmalloca ((argc + 1) * sizeof (char *));
+      argv = (const char **) xmalloca ((argc + 1) * sizeof (const char *));
 
       argp = argv;
       *argp++ = "mcs";
@@ -179,7 +179,7 @@ compile_csharp_using_mono (const char * const *sources,
               *argp++ = option;
             }
           else
-            *argp++ = (char *) source_file;
+            *argp++ = source_file;
         }
       *argp = NULL;
       /* Ensure argv length was correctly calculated.  */
@@ -232,10 +232,10 @@ compile_csharp_using_mono (const char * const *sources,
            i < 1 + (output_is_library ? 1 : 0)
                + 1 + libdirs_count + libraries_count;
            i++)
-        freea (argv[i]);
+        freea ((char *) argv[i]);
       for (i = 0; i < sources_count; i++)
         if (argv[argc - sources_count + i] != sources[i])
-          freea (argv[argc - sources_count + i]);
+          freea ((char *) argv[argc - sources_count + i]);
       freea (argv);
 
       return (exitstatus != 0);
@@ -263,7 +263,7 @@ compile_csharp_using_sscli (const char * const *sources,
       /* Test for presence of csc:
          "csc -help >/dev/null 2>/dev/null \
           && ! { csc -help 2>/dev/null | grep -i chicken > /dev/null; }"  */
-      char *argv[3];
+      const char *argv[3];
       pid_t child;
       int fd[1];
       int exitstatus;
@@ -312,20 +312,19 @@ compile_csharp_using_sscli (const char * const *sources,
   if (csc_present)
     {
       unsigned int argc;
-      char **argv;
-      char **argp;
+      const char **argv;
+      const char **argp;
       int exitstatus;
       unsigned int i;
 
       argc =
         1 + 1 + 1 + libdirs_count + libraries_count
         + (optimize ? 1 : 0) + (debug ? 1 : 0) + sources_count;
-      argv = (char **) xmalloca ((argc + 1) * sizeof (char *));
+      argv = (const char **) xmalloca ((argc + 1) * sizeof (const char *));
 
       argp = argv;
       *argp++ = "csc";
-      *argp++ =
-        (char *) (output_is_library ? "-target:library" : "-target:exe");
+      *argp++ = (output_is_library ? "-target:library" : "-target:exe");
       {
         char *option = (char *) xmalloca (5 + strlen (output_file) + 1);
         memcpy (option, "-out:", 5);
@@ -365,7 +364,7 @@ compile_csharp_using_sscli (const char * const *sources,
               *argp++ = option;
             }
           else
-            *argp++ = (char *) source_file;
+            *argp++ = source_file;
         }
       *argp = NULL;
       /* Ensure argv length was correctly calculated.  */
@@ -384,10 +383,10 @@ compile_csharp_using_sscli (const char * const *sources,
                             true, true, NULL);
 
       for (i = 2; i < 3 + libdirs_count + libraries_count; i++)
-        freea (argv[i]);
+        freea ((char *) argv[i]);
       for (i = 0; i < sources_count; i++)
         if (argv[argc - sources_count + i] != sources[i])
-          freea (argv[argc - sources_count + i]);
+          freea ((char *) argv[argc - sources_count + i]);
       freea (argv);
 
       return (exitstatus != 0);
diff --git a/lib/csharpexec.c b/lib/csharpexec.c
index 5e2aa2c753..b6fcc47333 100644
--- a/lib/csharpexec.c
+++ b/lib/csharpexec.c
@@ -100,7 +100,7 @@ execute_csharp_using_mono (const char *assembly_path,
     {
       /* Test for presence of mono:
          "mono --version >/dev/null 2>/dev/null"  */
-      char *argv[3];
+      const char *argv[3];
       int exitstatus;
 
       argv[0] = "mono";
@@ -116,7 +116,8 @@ execute_csharp_using_mono (const char *assembly_path,
   if (mono_present)
     {
       char *old_monopath;
-      char **argv = (char **) xmalloca ((2 + nargs + 1) * sizeof (char *));
+      const char **argv =
+        (const char **) xmalloca ((2 + nargs + 1) * sizeof (const char *));
       unsigned int i;
       bool err;
 
@@ -124,9 +125,9 @@ execute_csharp_using_mono (const char *assembly_path,
       old_monopath = set_monopath (libdirs, libdirs_count, false, verbose);
 
       argv[0] = "mono";
-      argv[1] = (char *) assembly_path;
+      argv[1] = assembly_path;
       for (i = 0; i <= nargs; i++)
-        argv[2 + i] = (char *) args[i];
+        argv[2 + i] = args[i];
 
       if (verbose)
         {
@@ -163,7 +164,7 @@ execute_csharp_using_sscli (const char *assembly_path,
     {
       /* Test for presence of clix:
          "clix >/dev/null 2>/dev/null ; test $? = 1"  */
-      char *argv[2];
+      const char *argv[2];
       int exitstatus;
 
       argv[0] = "clix";
@@ -178,7 +179,8 @@ execute_csharp_using_sscli (const char *assembly_path,
   if (clix_present)
     {
       char *old_clixpath;
-      char **argv = (char **) xmalloca ((2 + nargs + 1) * sizeof (char *));
+      const char **argv =
+        (const char **) xmalloca ((2 + nargs + 1) * sizeof (const char *));
       unsigned int i;
       bool err;
 
@@ -186,9 +188,9 @@ execute_csharp_using_sscli (const char *assembly_path,
       old_clixpath = set_clixpath (libdirs, libdirs_count, false, verbose);
 
       argv[0] = "clix";
-      argv[1] = (char *) assembly_path;
+      argv[1] = assembly_path;
       for (i = 0; i <= nargs; i++)
-        argv[2 + i] = (char *) args[i];
+        argv[2 + i] = args[i];
 
       if (verbose)
         {
diff --git a/lib/csharpexec.h b/lib/csharpexec.h
index c0bb441521..088ac06ffa 100644
--- a/lib/csharpexec.h
+++ b/lib/csharpexec.h
@@ -21,7 +21,7 @@
 #include <stdbool.h>
 
 typedef bool execute_fn (const char *progname,
-                         const char *prog_path, char **prog_argv,
+                         const char *prog_path, const char * const *prog_argv,
                          void *private_data);
 
 /* Execute a C# program.
diff --git a/lib/execute.c b/lib/execute.c
index 5821e82877..bdc0c0c016 100644
--- a/lib/execute.c
+++ b/lib/execute.c
@@ -97,7 +97,7 @@ nonintr_open (const char *pathname, int oflag, mode_t mode)
 
 int
 execute (const char *progname,
-         const char *prog_path, char **prog_argv,
+         const char *prog_path, const char * const *prog_argv,
          const char *directory,
          bool ignore_sigpipe,
          bool null_stdin, bool null_stdout, bool null_stderr,
@@ -158,10 +158,10 @@ execute (const char *progname,
 
   /* Native Windows API.  */
 
-  char *prog_argv_mem_to_free;
+  char *argv_mem_to_free;
 
-  prog_argv = prepare_spawn (prog_argv, &prog_argv_mem_to_free);
-  if (prog_argv == NULL)
+  const char **argv = prepare_spawn (prog_argv, &argv_mem_to_free);
+  if (argv == NULL)
     xalloc_die ();
 
   int exitcode = -1;
@@ -188,17 +188,17 @@ execute (const char *progname,
       HANDLE stderr_handle =
         (HANDLE) _get_osfhandle (null_stderr ? nulloutfd : STDERR_FILENO);
 
-      exitcode = spawnpvech (P_WAIT, prog_path, (const char **) (prog_argv + 1),
-                             (const char **) environ, directory,
+      exitcode = spawnpvech (P_WAIT, prog_path, argv + 1,
+                             (const char * const *) environ, directory,
                              stdin_handle, stdout_handle, stderr_handle);
       if (exitcode == -1 && errno == ENOEXEC)
         {
           /* prog is not a native executable.  Try to execute it as a
              shell script.  Note that prepare_spawn() has already prepended
-             a hidden element "sh.exe" to prog_argv.  */
-          prog_argv[1] = prog_path;
-          exitcode = spawnpvech (P_WAIT, prog_argv[0], (const char **) prog_argv,
-                                 (const char **) environ, directory,
+             a hidden element "sh.exe" to argv.  */
+          argv[1] = prog_path;
+          exitcode = spawnpvech (P_WAIT, argv[0], argv,
+                                 (const char * const *) environ, directory,
                                  stdin_handle, stdout_handle, stderr_handle);
         }
     }
@@ -208,8 +208,8 @@ execute (const char *progname,
     close (nulloutfd);
   if (nullinfd >= 0)
     close (nullinfd);
-  free (prog_argv);
-  free (prog_argv_mem_to_free);
+  free (argv);
+  free (argv_mem_to_free);
   free (prog_path_to_free);
 
   if (termsigp != NULL)
@@ -277,11 +277,11 @@ execute (const char *progname,
                          != 0)))
           || (err = (directory != NULL
                      ? posix_spawn (&child, prog_path, &actions,
-                                    attrs_allocated ? &attrs : NULL, prog_argv,
-                                    environ)
+                                    attrs_allocated ? &attrs : NULL,
+                                    (char * const *) prog_argv, environ)
                      : posix_spawnp (&child, prog_path, &actions,
-                                     attrs_allocated ? &attrs : NULL, prog_argv,
-                                     environ)))
+                                     attrs_allocated ? &attrs : NULL,
+                                     (char * const *) prog_argv, environ)))
              != 0))
     {
       if (actions_allocated)
diff --git a/lib/execute.h b/lib/execute.h
index 34fc989668..908d8c537a 100644
--- a/lib/execute.h
+++ b/lib/execute.h
@@ -46,7 +46,7 @@
    It is recommended that no signal is blocked or ignored while execute()
    is called.  See spawn-pipe.h for the reason.  */
 extern int execute (const char *progname,
-                    const char *prog_path, char **prog_argv,
+                    const char *prog_path, const char * const *prog_argv,
                     const char *directory,
                     bool ignore_sigpipe,
                     bool null_stdin, bool null_stdout, bool null_stderr,
diff --git a/lib/javacomp.c b/lib/javacomp.c
index c24bb69166..ca7a6fe658 100644
--- a/lib/javacomp.c
+++ b/lib/javacomp.c
@@ -288,7 +288,7 @@ compile_using_envjavac (const char *javac,
   bool err;
   unsigned int command_length;
   char *command;
-  char *argv[4];
+  const char *argv[4];
   int exitstatus;
   unsigned int i;
   char *p;
@@ -367,8 +367,8 @@ compile_using_gcj (const char * const *java_sources,
 {
   bool err;
   unsigned int argc;
-  char **argv;
-  char **argp;
+  const char **argv;
+  const char **argp;
   char *fsource_arg;
   char *ftarget_arg;
   int exitstatus;
@@ -378,7 +378,7 @@ compile_using_gcj (const char * const *java_sources,
     2 + (no_assert_option ? 1 : 0) + (fsource_option ? 1 : 0)
     + (ftarget_option ? 1 : 0) + (optimize ? 1 : 0) + (debug ? 1 : 0)
     + (directory != NULL ? 2 : 0) + java_sources_count;
-  argv = (char **) xmalloca ((argc + 1) * sizeof (char *));
+  argv = (const char **) xmalloca ((argc + 1) * sizeof (const char *));
 
   argp = argv;
   *argp++ = "gcj";
@@ -410,10 +410,10 @@ compile_using_gcj (const char * const *java_sources,
   if (directory != NULL)
     {
       *argp++ = "-d";
-      *argp++ = (char *) directory;
+      *argp++ = directory;
     }
   for (i = 0; i < java_sources_count; i++)
-    *argp++ = (char *) java_sources[i];
+    *argp++ = java_sources[i];
   *argp = NULL;
   /* Ensure argv length was correctly calculated.  */
   if (argp - argv != argc)
@@ -453,27 +453,27 @@ compile_using_javac (const char * const *java_sources,
 {
   bool err;
   unsigned int argc;
-  char **argv;
-  char **argp;
+  const char **argv;
+  const char **argp;
   int exitstatus;
   unsigned int i;
 
   argc =
     1 + (source_option ? 2 : 0) + (target_option ? 2 : 0) + (optimize ? 1 : 0)
     + (debug ? 1 : 0) + (directory != NULL ? 2 : 0) + java_sources_count;
-  argv = (char **) xmalloca ((argc + 1) * sizeof (char *));
+  argv = (const char **) xmalloca ((argc + 1) * sizeof (const char *));
 
   argp = argv;
   *argp++ = "javac";
   if (source_option)
     {
       *argp++ = "-source";
-      *argp++ = (char *) source_version;
+      *argp++ = source_version;
     }
   if (target_option)
     {
       *argp++ = "-target";
-      *argp++ = (char *) target_version;
+      *argp++ = target_version;
     }
   if (optimize)
     *argp++ = "-O";
@@ -482,10 +482,10 @@ compile_using_javac (const char * const *java_sources,
   if (directory != NULL)
     {
       *argp++ = "-d";
-      *argp++ = (char *) directory;
+      *argp++ = directory;
     }
   for (i = 0; i < java_sources_count; i++)
-    *argp++ = (char *) java_sources[i];
+    *argp++ = java_sources[i];
   *argp = NULL;
   /* Ensure argv length was correctly calculated.  */
   if (argp - argv != argc)
@@ -519,15 +519,15 @@ compile_using_jikes (const char * const *java_sources,
 {
   bool err;
   unsigned int argc;
-  char **argv;
-  char **argp;
+  const char **argv;
+  const char **argp;
   int exitstatus;
   unsigned int i;
 
   argc =
     1 + (optimize ? 1 : 0) + (debug ? 1 : 0) + (directory != NULL ? 2 : 0)
     + java_sources_count;
-  argv = (char **) xmalloca ((argc + 1) * sizeof (char *));
+  argv = (const char **) xmalloca ((argc + 1) * sizeof (const char *));
 
   argp = argv;
   *argp++ = "jikes";
@@ -538,10 +538,10 @@ compile_using_jikes (const char * const *java_sources,
   if (directory != NULL)
     {
       *argp++ = "-d";
-      *argp++ = (char *) directory;
+      *argp++ = directory;
     }
   for (i = 0; i < java_sources_count; i++)
-    *argp++ = (char *) java_sources[i];
+    *argp++ = java_sources[i];
   *argp = NULL;
   /* Ensure argv length was correctly calculated.  */
   if (argp - argv != argc)
@@ -635,7 +635,7 @@ is_envjavac_gcj (const char *javac)
          "$JAVAC --version 2>/dev/null | sed -e 1q | grep gcj > /dev/null"  */
       unsigned int command_length;
       char *command;
-      char *argv[4];
+      const char *argv[4];
       pid_t child;
       int fd[1];
       FILE *fp;
@@ -717,7 +717,7 @@ is_envjavac_gcj43 (const char *javac)
           | sed -e '/^4\.[012]/d' | grep '^[4-9]' >/dev/null"  */
       unsigned int command_length;
       char *command;
-      char *argv[4];
+      const char *argv[4];
       pid_t child;
       int fd[1];
       FILE *fp;
@@ -1406,7 +1406,7 @@ is_gcj_present (void)
          "gcj --version 2> /dev/null | \
           sed -e 's,^[^0-9]*,,' -e 1q | \
           sed -e '/^3\.[01]/d' | grep '^[3-9]' > /dev/null"  */
-      char *argv[3];
+      const char *argv[3];
       pid_t child;
       int fd[1];
       int exitstatus;
@@ -1522,7 +1522,7 @@ is_gcj_43 (void)
          "gcj --version 2> /dev/null | \
           sed -e 's,^[^0-9]*,,' -e 1q | \
           sed -e '/^4\.[012]/d' | grep '^[4-9]'"  */
-      char *argv[3];
+      const char *argv[3];
       pid_t child;
       int fd[1];
       int exitstatus;
@@ -1871,7 +1871,7 @@ is_javac_present (void)
   if (!javac_tested)
     {
       /* Test for presence of javac: "javac 2> /dev/null ; test $? -le 2"  */
-      char *argv[2];
+      const char *argv[2];
       int exitstatus;
 
       argv[0] = "javac";
@@ -2138,7 +2138,7 @@ is_jikes_present (void)
   if (!jikes_tested)
     {
       /* Test for presence of jikes: "jikes 2> /dev/null ; test $? = 1"  */
-      char *argv[2];
+      const char *argv[2];
       int exitstatus;
 
       argv[0] = "jikes";
diff --git a/lib/javaexec.c b/lib/javaexec.c
index d486fb8715..613c7fc7aa 100644
--- a/lib/javaexec.c
+++ b/lib/javaexec.c
@@ -96,7 +96,8 @@ execute_java_class (const char *class_name,
     {
       char *exe_pathname = xconcatenated_filename (exe_dir, class_name, EXEEXT);
       char *old_classpath;
-      char **argv = (char **) xmalloca ((1 + nargs + 1) * sizeof (char *));
+      const char **argv =
+        (const char **) xmalloca ((1 + nargs + 1) * sizeof (const char *));
       unsigned int i;
 
       /* Set CLASSPATH.  */
@@ -106,7 +107,7 @@ execute_java_class (const char *class_name,
 
       argv[0] = exe_pathname;
       for (i = 0; i <= nargs; i++)
-        argv[1 + i] = (char *) args[i];
+        argv[1 + i] = args[i];
 
       if (verbose)
         {
@@ -136,7 +137,7 @@ execute_java_class (const char *class_name,
         char *old_classpath;
         unsigned int command_length;
         char *command;
-        char *argv[4];
+        const char *argv[4];
         const char * const *arg;
         char *p;
 
@@ -202,7 +203,7 @@ execute_java_class (const char *class_name,
     if (!gij_tested)
       {
         /* Test for presence of gij: "gij --version > /dev/null"  */
-        char *argv[3];
+        const char *argv[3];
         int exitstatus;
 
         argv[0] = "gij";
@@ -218,7 +219,8 @@ execute_java_class (const char *class_name,
     if (gij_present)
       {
         char *old_classpath;
-        char **argv = (char **) xmalloca ((2 + nargs + 1) * sizeof (char *));
+        const char **argv =
+          (const char **) xmalloca ((2 + nargs + 1) * sizeof (const char *));
         unsigned int i;
 
         /* Set CLASSPATH.  */
@@ -227,9 +229,9 @@ execute_java_class (const char *class_name,
                          verbose);
 
         argv[0] = "gij";
-        argv[1] = (char *) class_name;
+        argv[1] = class_name;
         for (i = 0; i <= nargs; i++)
-          argv[2 + i] = (char *) args[i];
+          argv[2 + i] = args[i];
 
         if (verbose)
           {
@@ -256,7 +258,7 @@ execute_java_class (const char *class_name,
     if (!java_tested)
       {
         /* Test for presence of java: "java -version 2> /dev/null"  */
-        char *argv[3];
+        const char *argv[3];
         int exitstatus;
 
         argv[0] = "java";
@@ -272,7 +274,8 @@ execute_java_class (const char *class_name,
     if (java_present)
       {
         char *old_classpath;
-        char **argv = (char **) xmalloca ((2 + nargs + 1) * sizeof (char *));
+        const char **argv =
+          (const char **) xmalloca ((2 + nargs + 1) * sizeof (const char *));
         unsigned int i;
 
         /* Set CLASSPATH.  We don't use the "-classpath ..." option because
@@ -283,9 +286,9 @@ execute_java_class (const char *class_name,
                          verbose);
 
         argv[0] = "java";
-        argv[1] = (char *) class_name;
+        argv[1] = class_name;
         for (i = 0; i <= nargs; i++)
-          argv[2 + i] = (char *) args[i];
+          argv[2 + i] = args[i];
 
         if (verbose)
           {
@@ -312,7 +315,7 @@ execute_java_class (const char *class_name,
     if (!jre_tested)
       {
         /* Test for presence of jre: "jre 2> /dev/null ; test $? = 1"  */
-        char *argv[2];
+        const char *argv[2];
         int exitstatus;
 
         argv[0] = "jre";
@@ -327,7 +330,8 @@ execute_java_class (const char *class_name,
     if (jre_present)
       {
         char *old_classpath;
-        char **argv = (char **) xmalloca ((2 + nargs + 1) * sizeof (char *));
+        const char **argv =
+          (const char **) xmalloca ((2 + nargs + 1) * sizeof (const char *));
         unsigned int i;
 
         /* Set CLASSPATH.  We don't use the "-classpath ..." option because
@@ -338,9 +342,9 @@ execute_java_class (const char *class_name,
                          verbose);
 
         argv[0] = "jre";
-        argv[1] = (char *) class_name;
+        argv[1] = class_name;
         for (i = 0; i <= nargs; i++)
-          argv[2 + i] = (char *) args[i];
+          argv[2 + i] = args[i];
 
         if (verbose)
           {
@@ -369,7 +373,7 @@ execute_java_class (const char *class_name,
     if (!jview_tested)
       {
         /* Test for presence of jview: "jview -? >nul ; test $? = 1"  */
-        char *argv[3];
+        const char *argv[3];
         int exitstatus;
 
         argv[0] = "jview";
@@ -385,7 +389,8 @@ execute_java_class (const char *class_name,
     if (jview_present)
       {
         char *old_classpath;
-        char **argv = (char **) xmalloca ((2 + nargs + 1) * sizeof (char *));
+        const char **argv =
+          (const char **) xmalloca ((2 + nargs + 1) * sizeof (const char *));
         unsigned int i;
 
         /* Set CLASSPATH.  */
@@ -394,9 +399,9 @@ execute_java_class (const char *class_name,
                          verbose);
 
         argv[0] = "jview";
-        argv[1] = (char *) class_name;
+        argv[1] = class_name;
         for (i = 0; i <= nargs; i++)
-          argv[2 + i] = (char *) args[i];
+          argv[2 + i] = args[i];
 
         if (verbose)
           {
diff --git a/lib/javaexec.h b/lib/javaexec.h
index c17a6947ca..9480e73251 100644
--- a/lib/javaexec.h
+++ b/lib/javaexec.h
@@ -21,7 +21,7 @@
 #include <stdbool.h>
 
 typedef bool execute_fn (const char *progname,
-                         const char *prog_path, char **prog_argv,
+                         const char *prog_path, const char * const *prog_argv,
                          void *private_data);
 
 /* Execute a Java class.
diff --git a/lib/javaversion.c b/lib/javaversion.c
index e50c499c9b..2bfb08f662 100644
--- a/lib/javaversion.c
+++ b/lib/javaversion.c
@@ -52,7 +52,7 @@ struct locals
 
 static bool
 execute_and_read_line (const char *progname,
-                       const char *prog_path, char **prog_argv,
+                       const char *prog_path, const char * const *prog_argv,
                        void *private_data)
 {
   struct locals *l = (struct locals *) private_data;
diff --git a/lib/os2-spawn.c b/lib/os2-spawn.c
index 53a35f6dff..ac425a32d8 100644
--- a/lib/os2-spawn.c
+++ b/lib/os2-spawn.c
@@ -92,11 +92,11 @@ undup_safer_noinherit (int tempfd, int origfd)
     }
 }
 
-char **
-prepare_spawn (char **argv, char **mem_to_free)
+const char **
+prepare_spawn (const char * const *argv, char **mem_to_free)
 {
   size_t argc;
-  char **new_argv;
+  const char **new_argv;
   size_t i;
 
   /* Count number of arguments.  */
@@ -104,7 +104,7 @@ prepare_spawn (char **argv, char **mem_to_free)
     ;
 
   /* Allocate new argument vector.  */
-  new_argv = (char **) malloc ((1 + argc + 1) * sizeof (char *));
+  new_argv = (const char **) malloc ((1 + argc + 1) * sizeof (const char *));
   if (new_argv == NULL)
     return NULL;
 
diff --git a/lib/os2-spawn.h b/lib/os2-spawn.h
index 4c8c6a89fd..419f7f967d 100644
--- a/lib/os2-spawn.h
+++ b/lib/os2-spawn.h
@@ -27,6 +27,7 @@ extern int dup_safer_noinherit (int fd);
 extern void undup_safer_noinherit (int tempfd, int origfd);
 
 /* Prepares an argument vector before calling spawn().  */
-extern char ** prepare_spawn (char **argv, char **mem_to_free);
+extern const char ** prepare_spawn (const char * const *argv,
+                                    char **mem_to_free);
 
 #endif /* _OS2_SPAWN_H */
diff --git a/lib/pipe-filter-gi.c b/lib/pipe-filter-gi.c
index 7528053c6b..80617d7dec 100644
--- a/lib/pipe-filter-gi.c
+++ b/lib/pipe-filter-gi.c
@@ -485,7 +485,7 @@ filter_retcode (struct pipe_filter_gi *filter)
 
 struct pipe_filter_gi *
 pipe_filter_gi_create (const char *progname,
-                       const char *prog_path, const char **prog_argv,
+                       const char *prog_path, const char * const *prog_argv,
                        bool null_stderr, bool exit_on_error,
                        prepare_read_fn prepare_read,
                        done_read_fn done_read,
@@ -497,7 +497,7 @@ pipe_filter_gi_create (const char *progname,
     (struct pipe_filter_gi *) xmalloc (sizeof (struct pipe_filter_gi));
 
   /* Open a bidirectional pipe to a subprocess.  */
-  filter->child = create_pipe_bidi (progname, prog_path, (char **) prog_argv,
+  filter->child = create_pipe_bidi (progname, prog_path, prog_argv,
                                     NULL, null_stderr, true, exit_on_error,
                                     filter->fd);
   filter->progname = progname;
diff --git a/lib/pipe-filter-ii.c b/lib/pipe-filter-ii.c
index 384a59bf68..2342088c10 100644
--- a/lib/pipe-filter-ii.c
+++ b/lib/pipe-filter-ii.c
@@ -255,7 +255,7 @@ reader_thread_func (void *thread_arg)
 
 int
 pipe_filter_ii_execute (const char *progname,
-                        const char *prog_path, const char **prog_argv,
+                        const char *prog_path, const char * const *prog_argv,
                         bool null_stderr, bool exit_on_error,
                         prepare_write_fn prepare_write,
                         done_write_fn done_write,
@@ -270,7 +270,7 @@ pipe_filter_ii_execute (const char *progname,
 #endif
 
   /* Open a bidirectional pipe to a subprocess.  */
-  child = create_pipe_bidi (progname, prog_path, (char **) prog_argv,
+  child = create_pipe_bidi (progname, prog_path, prog_argv,
                             NULL, null_stderr, true, exit_on_error,
                             fd);
   if (child == -1)
diff --git a/lib/pipe-filter.h b/lib/pipe-filter.h
index 9e2c966a5f..71ef70b387 100644
--- a/lib/pipe-filter.h
+++ b/lib/pipe-filter.h
@@ -133,7 +133,8 @@ typedef void (*done_read_fn) (void *data_read, size_t num_bytes_read,
    - the positive exit code of the subprocess if that failed.  */
 extern int
        pipe_filter_ii_execute (const char *progname,
-                               const char *prog_path, const char **prog_argv,
+                               const char *prog_path,
+                               const char * const *prog_argv,
                                bool null_stderr, bool exit_on_error,
                                prepare_write_fn prepare_write,
                                done_write_fn done_write,
@@ -179,7 +180,8 @@ struct pipe_filter_gi;
    Return the freshly created 'struct pipe_filter_gi'.  */
 extern struct pipe_filter_gi *
        pipe_filter_gi_create (const char *progname,
-                              const char *prog_path, const char **prog_argv,
+                              const char *prog_path,
+                              const char * const *prog_argv,
                               bool null_stderr, bool exit_on_error,
                               prepare_read_fn prepare_read,
                               done_read_fn done_read,
diff --git a/lib/sh-quote.c b/lib/sh-quote.c
index 1508d4e465..8181c7a25e 100644
--- a/lib/sh-quote.c
+++ b/lib/sh-quote.c
@@ -69,11 +69,11 @@ shell_quote (const char *string)
 /* Returns a freshly allocated string containing all argument strings, quoted,
    separated through spaces.  */
 char *
-shell_quote_argv (char * const *argv)
+shell_quote_argv (const char * const *argv)
 {
   if (*argv != NULL)
     {
-      char * const *argp;
+      const char * const *argp;
       size_t length;
       char *command;
       char *p;
diff --git a/lib/sh-quote.h b/lib/sh-quote.h
index 8b06355835..9c6f2aa82a 100644
--- a/lib/sh-quote.h
+++ b/lib/sh-quote.h
@@ -40,7 +40,7 @@ extern char * shell_quote (const char *string);
 
 /* Returns a freshly allocated string containing all argument strings, quoted,
    separated through spaces.  */
-extern char * shell_quote_argv (char * const *argv);
+extern char * shell_quote_argv (const char * const *argv);
 
 #ifdef __cplusplus
 }
diff --git a/lib/spawn-pipe.c b/lib/spawn-pipe.c
index c73872bf82..ba07d20ebc 100644
--- a/lib/spawn-pipe.c
+++ b/lib/spawn-pipe.c
@@ -123,7 +123,8 @@ nonintr_open (const char *pathname, int oflag, mode_t mode)
  */
 static pid_t
 create_pipe (const char *progname,
-             const char *prog_path, char **prog_argv,
+             const char *prog_path,
+             const char * const *prog_argv,
              const char *directory,
              bool pipe_stdin, bool pipe_stdout,
              const char *prog_stdin, const char *prog_stdout,
@@ -187,7 +188,7 @@ create_pipe (const char *progname,
      using the low-level functions CreatePipe(), DuplicateHandle(),
      CreateProcess() and _open_osfhandle(); see the GNU make and GNU clisp
      and cvs source code.  */
-  char *prog_argv_mem_to_free;
+  char *argv_mem_to_free;
   int ifd[2];
   int ofd[2];
   int child;
@@ -195,8 +196,8 @@ create_pipe (const char *progname,
   int stdinfd;
   int stdoutfd;
 
-  prog_argv = prepare_spawn (prog_argv, &prog_argv_mem_to_free);
-  if (prog_argv == NULL)
+  const char **argv = prepare_spawn (prog_argv, &argv_mem_to_free);
+  if (argv == NULL)
     xalloc_die ();
 
   if (pipe_stdout)
@@ -281,17 +282,17 @@ create_pipe (const char *progname,
       HANDLE stderr_handle =
         (HANDLE) _get_osfhandle (null_stderr ? nulloutfd : STDERR_FILENO);
 
-      child = spawnpvech (P_NOWAIT, prog_path, (const char **) (prog_argv + 1),
-                          (const char **) environ, directory,
+      child = spawnpvech (P_NOWAIT, prog_path, argv + 1,
+                          (const char * const *) environ, directory,
                           stdin_handle, stdout_handle, stderr_handle);
       if (child == -1 && errno == ENOEXEC)
         {
           /* prog is not a native executable.  Try to execute it as a
              shell script.  Note that prepare_spawn() has already prepended
-             a hidden element "sh.exe" to prog_argv.  */
-          prog_argv[1] = prog_path;
-          child = spawnpvech (P_NOWAIT, prog_argv[0], (const char **) prog_argv,
-                              (const char **) environ, directory,
+             a hidden element "sh.exe" to argv.  */
+          argv[1] = prog_path;
+          child = spawnpvech (P_NOWAIT, argv[0], argv,
+                              (const char * const *) environ, directory,
                               stdin_handle, stdout_handle, stderr_handle);
         }
     }
@@ -357,14 +358,14 @@ create_pipe (const char *progname,
        but it inherits all open()ed or dup2()ed file handles (which is what
        we want in the case of STD*_FILENO).  */
     {
-      child = _spawnvpe (P_NOWAIT, prog_path, (const char **) (prog_argv + 1),
+      child = _spawnvpe (P_NOWAIT, prog_path, argv + 1,
                          (const char **) environ);
       if (child == -1 && errno == ENOEXEC)
         {
           /* prog is not a native executable.  Try to execute it as a
              shell script.  Note that prepare_spawn() has already prepended
-             a hidden element "sh.exe" to prog_argv.  */
-          child = _spawnvpe (P_NOWAIT, prog_argv[0], (const char **) prog_argv,
+             a hidden element "sh.exe" to argv.  */
+          child = _spawnvpe (P_NOWAIT, argv[0], argv,
                              (const char **) environ);
         }
     }
@@ -391,8 +392,8 @@ create_pipe (const char *progname,
     close (ifd[1]);
 # endif
 
-  free (prog_argv);
-  free (prog_argv_mem_to_free);
+  free (argv);
+  free (argv_mem_to_free);
   free (prog_path_to_free);
 
   if (child == -1)
@@ -501,11 +502,11 @@ create_pipe (const char *progname,
                          != 0)))
           || (err = (directory != NULL
                      ? posix_spawn (&child, prog_path, &actions,
-                                    attrs_allocated ? &attrs : NULL, prog_argv,
-                                    environ)
+                                    attrs_allocated ? &attrs : NULL,
+                                    (char * const *) prog_argv, environ)
                      : posix_spawnp (&child, prog_path, &actions,
-                                     attrs_allocated ? &attrs : NULL, prog_argv,
-                                     environ)))
+                                     attrs_allocated ? &attrs : NULL,
+                                     (char * const *) prog_argv, environ)))
              != 0))
     {
       if (actions_allocated)
@@ -570,7 +571,7 @@ create_pipe (const char *progname,
  */
 pid_t
 create_pipe_bidi (const char *progname,
-                  const char *prog_path, char **prog_argv,
+                  const char *prog_path, const char * const *prog_argv,
                   const char *directory,
                   bool null_stderr,
                   bool slave_process, bool exit_on_error,
@@ -592,7 +593,7 @@ create_pipe_bidi (const char *progname,
  */
 pid_t
 create_pipe_in (const char *progname,
-                const char *prog_path, char **prog_argv,
+                const char *prog_path, const char * const *prog_argv,
                 const char *directory,
                 const char *prog_stdin, bool null_stderr,
                 bool slave_process, bool exit_on_error,
@@ -617,7 +618,7 @@ create_pipe_in (const char *progname,
  */
 pid_t
 create_pipe_out (const char *progname,
-                 const char *prog_path, char **prog_argv,
+                 const char *prog_path, const char * const *prog_argv,
                  const char *directory,
                  const char *prog_stdout, bool null_stderr,
                  bool slave_process, bool exit_on_error,
diff --git a/lib/spawn-pipe.h b/lib/spawn-pipe.h
index 02856a81b7..a624822578 100644
--- a/lib/spawn-pipe.h
+++ b/lib/spawn-pipe.h
@@ -96,7 +96,8 @@ extern "C" {
  * signal and the EPIPE error code.
  */
 extern pid_t create_pipe_out (const char *progname,
-                              const char *prog_path, char **prog_argv,
+                              const char *prog_path,
+                              const char * const *prog_argv,
                               const char *directory,
                               const char *prog_stdout, bool null_stderr,
                               bool slave_process, bool exit_on_error,
@@ -110,7 +111,8 @@ extern pid_t create_pipe_out (const char *progname,
  *
  */
 extern pid_t create_pipe_in (const char *progname,
-                             const char *prog_path, char **prog_argv,
+                             const char *prog_path,
+                             const char * const *prog_argv,
                              const char *directory,
                              const char *prog_stdin, bool null_stderr,
                              bool slave_process, bool exit_on_error,
@@ -139,7 +141,8 @@ extern pid_t create_pipe_in (const char *progname,
  *    input.  But you are currently busy reading from it.
  */
 extern pid_t create_pipe_bidi (const char *progname,
-                               const char *prog_path, char **prog_argv,
+                               const char *prog_path,
+                               const char * const *prog_argv,
                                const char *directory,
                                bool null_stderr,
                                bool slave_process, bool exit_on_error,
diff --git a/lib/windows-spawn.c b/lib/windows-spawn.c
index d252f32980..88a6b4dba4 100644
--- a/lib/windows-spawn.c
+++ b/lib/windows-spawn.c
@@ -122,11 +122,11 @@ quoted_arg_string (const char *string, char *mem)
   return p;
 }
 
-char **
-prepare_spawn (char **argv, char **mem_to_free)
+const char **
+prepare_spawn (const char * const *argv, char **mem_to_free)
 {
   size_t argc;
-  char **new_argv;
+  const char **new_argv;
   size_t i;
 
   /* Count number of arguments.  */
@@ -134,7 +134,7 @@ prepare_spawn (char **argv, char **mem_to_free)
     ;
 
   /* Allocate new argument vector.  */
-  new_argv = (char **) malloc ((1 + argc + 1) * sizeof (char *));
+  new_argv = (const char **) malloc ((1 + argc + 1) * sizeof (const char *));
 
   /* Add an element upfront that can be used when argv[0] turns out to be a
      script, not a program.
diff --git a/lib/windows-spawn.h b/lib/windows-spawn.h
index ddbbffa0be..77720d5559 100644
--- a/lib/windows-spawn.h
+++ b/lib/windows-spawn.h
@@ -62,7 +62,8 @@
    allocated as well.  In case of memory allocation failure, NULL is returned,
    with errno set.
  */
-extern char ** prepare_spawn (char **argv, char **mem_to_free);
+extern const char ** prepare_spawn (const char * const *argv,
+                                    char **mem_to_free);
 
 /* Creates a subprocess.
    MODE is either P_WAIT or P_NOWAIT.