Use `const char *` instead of `char *` for line parameter for process callbacks.

This patch changes the type definition of the process callbacks to use
`const char *` instead of `char *`.

See: https://bugs.torproject.org/28179

src/feature/client/transports.c

@@ -1711,7 +1711,9 @@ tor_escape_str_for_pt_args(const char *string, const char *chars_to_escape)
  * stdout. Our process can be found in <b>process</b>, the data can be found in
  * <b>line</b> and the length of our line is given in <b>size</b>. */
 STATIC void
-managed_proxy_stdout_callback(process_t *process, char *line, size_t size)
+managed_proxy_stdout_callback(process_t *process,
+                              const char *line,
+                              size_t size)
 {
   tor_assert(process);
   tor_assert(line);
@@ -1732,7 +1734,9 @@ managed_proxy_stdout_callback(process_t *process, char *line, size_t size)
  * stderr. Our process can be found in <b>process</b>, the data can be found in
  * <b>line</b> and the length of our line is given in <b>size</b>. */
 STATIC void
-managed_proxy_stderr_callback(process_t *process, char *line, size_t size)
+managed_proxy_stderr_callback(process_t *process,
+                              const char *line,
+                              size_t size)
 {
   tor_assert(process);
   tor_assert(line);

src/feature/client/transports.h

@@ -143,8 +143,8 @@ STATIC char* get_pt_proxy_uri(void);
 
 STATIC void free_execve_args(char **arg);
 
-STATIC void managed_proxy_stdout_callback(process_t *, char *, size_t);
-STATIC void managed_proxy_stderr_callback(process_t *, char *, size_t);
+STATIC void managed_proxy_stdout_callback(process_t *, const char *, size_t);
+STATIC void managed_proxy_stderr_callback(process_t *, const char *, size_t);
 STATIC bool managed_proxy_exit_callback(process_t *, process_exit_code_t);
 
 #endif /* defined(PT_PRIVATE) */

src/lib/process/process.h

@@ -54,7 +54,7 @@ typedef uint64_t process_exit_code_t;
 typedef uint64_t process_pid_t;
 
 typedef void (*process_read_callback_t)(process_t *,
-                                        char *,
+                                        const char *,
                                         size_t);
 typedef bool
 (*process_exit_callback_t)(process_t *, process_exit_code_t);

src/test/test_process.c

@@ -98,7 +98,7 @@ process_mocked_write_stdin(process_t *process, buf_t *buffer)
 }
 
 static void
-process_stdout_callback(process_t *process, char *data, size_t size)
+process_stdout_callback(process_t *process, const char *data, size_t size)
 {
   tt_ptr_op(process, OP_NE, NULL);
   tt_ptr_op(data, OP_NE, NULL);
@@ -112,7 +112,7 @@ process_stdout_callback(process_t *process, char *data, size_t size)
 }
 
 static void
-process_stderr_callback(process_t *process, char *data, size_t size)
+process_stderr_callback(process_t *process, const char *data, size_t size)
 {
   tt_ptr_op(process, OP_NE, NULL);
   tt_ptr_op(data, OP_NE, NULL);

src/test/test_process_slow.c

@@ -67,7 +67,7 @@ process_data_free(process_data_t *process_data)
 }
 
 static void
-process_stdout_callback(process_t *process, char *data, size_t size)
+process_stdout_callback(process_t *process, const char *data, size_t size)
 {
   tt_ptr_op(process, OP_NE, NULL);
   tt_ptr_op(data, OP_NE, NULL);
@@ -81,7 +81,7 @@ process_stdout_callback(process_t *process, char *data, size_t size)
 }
 
 static void
-process_stderr_callback(process_t *process, char *data, size_t size)
+process_stderr_callback(process_t *process, const char *data, size_t size)
 {
   tt_ptr_op(process, OP_NE, NULL);
   tt_ptr_op(data, OP_NE, NULL);