[PATCH v2 21/31] Use ui_file_as_string in gdb/compile/

Pedro Alves palves@redhat.com
Wed Oct 19 23:48:00 GMT 2016


On 10/20/2016 12:08 AM, Simon Marchi wrote:
> The doc for get_new_file_names should probably be updated:
> 
> /* Compute the names of source and object files to use.  The names are
>    allocated by malloc and should be freed by the caller.  */
> 
>>  static void
>> -get_new_file_names (char **source_file, char **object_file)
>> +get_new_file_names (std::string *source_file, std::string *object_file)
>>  {
> 
> 
> Same for compile_to_object, both for the "freeing" part and the part
> that talks about the return value.
> 
> We should use $other_language instead of C++, to be able to do
> 
>   source_filep, object_filep = compile_to_object (...)
> 
> :)

Well, there's std::pair in C++03, and std::tuple in C++11.
And C++17 has structured bindings:

  auto [source_file, object_file] = compile_to_object ();

:-)

But I think returning a real named struct is clearer than all that.
See patch below showing the idea.  WDYT?

> 
> Btw, would it be good to use references for those strings?

Maybe.  I had kept it using pointers to make it clearer at the
call site that these are output parameters.  Maybe that's
old-school C++ mentality?  That moot with this version of the
patch though, so I can dodge discussing that for now.  :-)

> 
>>     error condition, error () is called.  The caller is responsible for
>>     freeing both strings.  */
>>
>> -static char *
>> +static void
>>  compile_to_object (struct command_line *cmd, const char *cmd_string,
>>             enum compile_i_scope_types scope,
>> -           char **source_filep)
>> +           std::string *source_filep,
>> +           std::string *object_filep)
>>  {
> 
> ...
> 
>> @@ -609,30 +606,27 @@ void
>>  eval_compile_command (struct command_line *cmd, const char *cmd_string,
>>                enum compile_i_scope_types scope, void *scope_data)
>>  {
>> -  char *object_file, *source_file;
>> +  std::string source_file, object_file;
>>
>> -  object_file = compile_to_object (cmd, cmd_string, scope,
>> &source_file);
>> -  if (object_file != NULL)
>> +  compile_to_object (cmd, cmd_string, scope, &source_file,
>> &object_file);
>> +  if (!object_file.empty ())
> 
> Can this actually happen?

Hmm, looks like not.

This passes the gdb.compile/ tests.

>From 80470a5ac4b3db444f2bc605a639ca6ef795f743 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Thu, 20 Oct 2016 00:28:26 +0100
Subject: [PATCH] Use ui_file_as_string in gdb/compile/

gdb/ChangeLog:
yyyy-mm-yy  Pedro Alves  <palves@redhat.com>

	* c-lang.h (c_compute_program): Now returns std::string.
	* compile/compile-c-support.c (c_compute_program): Now returns a
	std::string.  Use ui_file_as_string.
	* compile/compile.c (get_new_file_names): Change output parameters
	to std::string pointers.  Use string_printf.
	(compile_to_object): Change output parameters to std::string
	pointers.  Use ui_file_as_string.
	(eval_compile_command): Use std::string.
	* language.h (struct language_defn) <la_compute_program>: Now
	returns std::string.
---
 gdb/c-lang.h                    |  14 ++---
 gdb/compile/compile-c-support.c |   6 +-
 gdb/compile/compile.c           | 132 ++++++++++++++++++++++------------------
 gdb/language.h                  |  14 ++---
 4 files changed, 89 insertions(+), 77 deletions(-)

diff --git a/gdb/c-lang.h b/gdb/c-lang.h
index 12be8bf..8378d4f 100644
--- a/gdb/c-lang.h
+++ b/gdb/c-lang.h
@@ -152,16 +152,16 @@ extern int c_textual_element_type (struct type *, char);
 
 extern struct compile_instance *c_get_compile_context (void);
 
-/* This takes the user-supplied text and returns a newly malloc'd bit
-   of code to compile.
+/* This takes the user-supplied text and returns a new bit of code to
+   compile.
 
    This is used as the la_compute_program language method; see that
    for a description of the arguments.  */
 
-extern char *c_compute_program (struct compile_instance *inst,
-				const char *input,
-				struct gdbarch *gdbarch,
-				const struct block *expr_block,
-				CORE_ADDR expr_pc);
+extern std::string c_compute_program (struct compile_instance *inst,
+				      const char *input,
+				      struct gdbarch *gdbarch,
+				      const struct block *expr_block,
+				      CORE_ADDR expr_pc);
 
 #endif /* !defined (C_LANG_H) */
diff --git a/gdb/compile/compile-c-support.c b/gdb/compile/compile-c-support.c
index c42daba..641b0fd 100644
--- a/gdb/compile/compile-c-support.c
+++ b/gdb/compile/compile-c-support.c
@@ -326,7 +326,7 @@ generate_register_struct (struct ui_file *stream, struct gdbarch *gdbarch,
    to the inferior when the expression was created, and EXPR_PC
    indicates the value of $PC.  */
 
-char *
+std::string
 c_compute_program (struct compile_instance *inst,
 		   const char *input,
 		   struct gdbarch *gdbarch,
@@ -334,7 +334,7 @@ c_compute_program (struct compile_instance *inst,
 		   CORE_ADDR expr_pc)
 {
   struct ui_file *buf, *var_stream = NULL;
-  char *code;
+  std::string code;
   struct cleanup *cleanup;
   struct compile_c_instance *context = (struct compile_c_instance *) inst;
 
@@ -435,7 +435,7 @@ c_compute_program (struct compile_instance *inst,
     fputs_unfiltered ("}\n", buf);
 
   add_code_footer (inst->scope, buf);
-  code = ui_file_xstrdup (buf, NULL);
+  code = ui_file_as_string (buf);
   do_cleanups (cleanup);
   return code;
 }
diff --git a/gdb/compile/compile.c b/gdb/compile/compile.c
index 0c4a738..08dfdc2 100644
--- a/gdb/compile/compile.c
+++ b/gdb/compile/compile.c
@@ -255,18 +255,40 @@ get_compile_file_tempdir (void)
   return tempdir_name;
 }
 
-/* Compute the names of source and object files to use.  The names are
-   allocated by malloc and should be freed by the caller.  */
-
-static void
-get_new_file_names (char **source_file, char **object_file)
+class compile_file_names
+{
+public:
+  compile_file_names(std::string source_file, std::string object_file)
+    : m_source_file (source_file), m_object_file (object_file)
+  {}
+
+  const char *source_file ()
+  {
+    return m_source_file.c_str ();
+  }
+
+  const char *object_file ()
+  {
+    return m_object_file.c_str ();
+  }
+
+private:
+  std::string m_source_file;
+  std::string m_object_file;
+};
+
+/* Compute the names of source and object files to use.  */
+
+static compile_file_names
+get_new_file_names ()
 {
   static int seq;
   const char *dir = get_compile_file_tempdir ();
 
   ++seq;
-  *source_file = xstrprintf ("%s%sout%d.c", dir, SLASH_STRING, seq);
-  *object_file = xstrprintf ("%s%sout%d.o", dir, SLASH_STRING, seq);
+
+  return compile_file_names (string_printf ("%s%sout%d.c", dir, SLASH_STRING, seq),
+			     string_printf ("%s%sout%d.o", dir, SLASH_STRING, seq));
 }
 
 /* Get the block and PC at which to evaluate an expression.  */
@@ -456,18 +478,13 @@ print_callback (void *ignore, const char *message)
 }
 
 /* Process the compilation request.  On success it returns the object
-   file name and *SOURCE_FILEP is set to source file name.  On an
-   error condition, error () is called.  The caller is responsible for
-   freeing both strings.  */
+   and source file names.  On an error condition, error () is
+   called.  */
 
-static char *
+static compile_file_names
 compile_to_object (struct command_line *cmd, const char *cmd_string,
-		   enum compile_i_scope_types scope,
-		   char **source_filep)
+		   enum compile_i_scope_types scope)
 {
-  char *code;
-  const char *input;
-  char *source_file, *object_file;
   struct compile_instance *compiler;
   struct cleanup *cleanup, *inner_cleanup;
   const struct block *expr_block;
@@ -503,11 +520,14 @@ compile_to_object (struct command_line *cmd, const char *cmd_string,
 
   /* From the provided expression, build a scope to pass to the
      compiler.  */
+
+  std::string input_buf;
+  const char *input;
+
   if (cmd != NULL)
     {
       struct ui_file *stream = mem_fileopen ();
       struct command_line *iter;
-      char *stream_buf;
 
       make_cleanup_ui_file_delete (stream);
       for (iter = cmd->body_list[0]; iter; iter = iter->next)
@@ -516,20 +536,19 @@ compile_to_object (struct command_line *cmd, const char *cmd_string,
 	  fputs_unfiltered ("\n", stream);
 	}
 
-      stream_buf = ui_file_xstrdup (stream, NULL);
-      make_cleanup (xfree, stream_buf);
-      input = stream_buf;
+      input_buf = ui_file_as_string (stream);
+      input = input_buf.c_str ();
     }
   else if (cmd_string != NULL)
     input = cmd_string;
   else
     error (_("Neither a simple expression, or a multi-line specified."));
 
-  code = current_language->la_compute_program (compiler, input, gdbarch,
-					       expr_block, expr_pc);
-  make_cleanup (xfree, code);
+  std::string code
+    = current_language->la_compute_program (compiler, input, gdbarch,
+					    expr_block, expr_pc);
   if (compile_debug)
-    fprintf_unfiltered (gdb_stdlog, "debug output:\n\n%s", code);
+    fprintf_unfiltered (gdb_stdlog, "debug output:\n\n%s", code.c_str ());
 
   os_rx = osabi_triplet_regexp (gdbarch_osabi (gdbarch));
   arch_rx = gdbarch_gnu_triplet_regexp (gdbarch);
@@ -560,37 +579,36 @@ compile_to_object (struct command_line *cmd, const char *cmd_string,
 			    argi, argv[argi]);
     }
 
-  get_new_file_names (&source_file, &object_file);
-  inner_cleanup = make_cleanup (xfree, source_file);
-  make_cleanup (xfree, object_file);
+  compile_file_names fnames = get_new_file_names ();
 
-  src = gdb_fopen_cloexec (source_file, "w");
+  src = gdb_fopen_cloexec (fnames.source_file (), "w");
   if (src == NULL)
     perror_with_name (_("Could not open source file for writing"));
-  make_cleanup (cleanup_unlink_file, source_file);
-  if (fputs (code, src) == EOF)
+  inner_cleanup = make_cleanup (cleanup_unlink_file,
+				(void *) fnames.source_file ());
+  if (fputs (code.c_str (), src) == EOF)
     perror_with_name (_("Could not write to source file"));
   fclose (src);
 
   if (compile_debug)
     fprintf_unfiltered (gdb_stdlog, "source file produced: %s\n\n",
-			source_file);
+			fnames.source_file ());
 
   /* Call the compiler and start the compilation process.  */
-  compiler->fe->ops->set_source_file (compiler->fe, source_file);
+  compiler->fe->ops->set_source_file (compiler->fe, fnames.source_file ());
 
-  if (!compiler->fe->ops->compile (compiler->fe, object_file,
+  if (!compiler->fe->ops->compile (compiler->fe, fnames.object_file (),
 				   compile_debug))
     error (_("Compilation failed."));
 
   if (compile_debug)
     fprintf_unfiltered (gdb_stdlog, "object file produced: %s\n\n",
-			object_file);
+			fnames.object_file ());
 
   discard_cleanups (inner_cleanup);
   do_cleanups (cleanup);
-  *source_filep = source_file;
-  return object_file;
+
+  return fnames;
 }
 
 /* The "compile" prefix command.  */
@@ -609,32 +627,26 @@ void
 eval_compile_command (struct command_line *cmd, const char *cmd_string,
 		      enum compile_i_scope_types scope, void *scope_data)
 {
-  char *object_file, *source_file;
-
-  object_file = compile_to_object (cmd, cmd_string, scope, &source_file);
-  if (object_file != NULL)
+  struct cleanup *cleanup_unlink;
+  struct compile_module *compile_module;
+
+  compile_file_names fnames = compile_to_object (cmd, cmd_string, scope);
+
+  cleanup_unlink = make_cleanup (cleanup_unlink_file,
+				 (void *) fnames.object_file ());
+  make_cleanup (cleanup_unlink_file, (void *) fnames.source_file ());
+  compile_module = compile_object_load (fnames.object_file (),
+					fnames.source_file (),
+					scope, scope_data);
+  if (compile_module == NULL)
     {
-      struct cleanup *cleanup_xfree, *cleanup_unlink;
-      struct compile_module *compile_module;
-
-      cleanup_xfree = make_cleanup (xfree, object_file);
-      make_cleanup (xfree, source_file);
-      cleanup_unlink = make_cleanup (cleanup_unlink_file, object_file);
-      make_cleanup (cleanup_unlink_file, source_file);
-      compile_module = compile_object_load (object_file, source_file,
-					    scope, scope_data);
-      if (compile_module == NULL)
-	{
-	  gdb_assert (scope == COMPILE_I_PRINT_ADDRESS_SCOPE);
-	  do_cleanups (cleanup_xfree);
-	  eval_compile_command (cmd, cmd_string,
-				COMPILE_I_PRINT_VALUE_SCOPE, scope_data);
-	  return;
-	}
-      discard_cleanups (cleanup_unlink);
-      do_cleanups (cleanup_xfree);
-      compile_object_run (compile_module);
+      gdb_assert (scope == COMPILE_I_PRINT_ADDRESS_SCOPE);
+      eval_compile_command (cmd, cmd_string,
+			    COMPILE_I_PRINT_VALUE_SCOPE, scope_data);
+      return;
     }
+  discard_cleanups (cleanup_unlink);
+  compile_object_run (compile_module);
 }
 
 /* See compile/compile-internal.h.  */
diff --git a/gdb/language.h b/gdb/language.h
index d6f932e..758f265 100644
--- a/gdb/language.h
+++ b/gdb/language.h
@@ -406,8 +406,8 @@ struct language_defn
        If 'la_get_gcc_context' is not defined, then this method is
        ignored.
 
-       This takes the user-supplied text and returns a newly malloc'd
-       bit of code to compile.  The caller owns the result.
+       This takes the user-supplied text and returns a new bit of code
+       to compile.
 
        INST is the compiler instance being used.
        INPUT is the user's input text.
@@ -416,11 +416,11 @@ struct language_defn
        parsed.
        EXPR_PC is the PC at which the expression is being parsed.  */
 
-    char *(*la_compute_program) (struct compile_instance *inst,
-				 const char *input,
-				 struct gdbarch *gdbarch,
-				 const struct block *expr_block,
-				 CORE_ADDR expr_pc);
+    std::string (*la_compute_program) (struct compile_instance *inst,
+				       const char *input,
+				       struct gdbarch *gdbarch,
+				       const struct block *expr_block,
+				       CORE_ADDR expr_pc);
 
     /* Add fields above this point, so the magic number is always last.  */
     /* Magic number for compat checking.  */
-- 
2.5.5




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