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Exported const objects 

const works different in C vs C++.  In C++, a global "const" variable
has internal linkage by default, resulting in link errors like:

  ...
  extension.o: In function `get_ext_lang_defn(extension_language)':
  gdb/extension.c:126: undefined reference to `extension_language_guile'
  gdb/extension.c:124: undefined reference to `extension_language_guile'
  ...

The fix is to define exported const objects with "extern const".  But
that in C would not be a definition.  So we need to #ifdef C vs C++ in
this case.

EXPORTED_CONST comes from include/ansidecl.h, but in the
feature_to_c.sh case I think it's better to leave the script with no
dependencies.

gdb/ChangeLog:
2015-02-27  Pedro Alves  <palves@redhat.com>

	* cp-valprint.c (vtbl_ptr_name): Use EXPORTED_CONST.
	* guile/guile.c (extension_language_guile): Use EXPORTED_CONST.
	* features/feature_to_c.sh: Tag the generated xml_builtin array
	with extern const in C++ mode.
This commit is contained in:
Pedro Alves 2015-02-09 13:22:27 +00:00
parent 1424c16eab
commit 7cf99fb1c7
4 changed files with 16 additions and 3 deletions
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7
gdb/ChangeLog
View File

@ -1,3 +1,10 @@
2015-02-27 Pedro Alves <palves@redhat.com>
* cp-valprint.c (vtbl_ptr_name): Use EXPORTED_CONST.
* guile/guile.c (extension_language_guile): Use EXPORTED_CONST.
* features/feature_to_c.sh: Tag the generated xml_builtin array
with extern const in C++ mode.
2015-02-27 Tom Tromey <tromey@redhat.com>
* minidebug.c (struct lzma_stream): Rename to ...

2
gdb/cp-valprint.c
View File

@ -88,7 +88,7 @@ static void cp_print_value (struct type *, struct type *,
/* GCC versions after 2.4.5 use this. */
const char vtbl_ptr_name[] = "__vtbl_ptr_type";
EXPORTED_CONST char vtbl_ptr_name[] = "__vtbl_ptr_type";
/* Return truth value for assertion that TYPE is of the type
"pointer to virtual function". */

8
gdb/features/feature_to_c.sh
View File

@ -63,7 +63,13 @@ for input; do
done
echo >> $output
echo "const char *const xml_builtin[][2] = {" >> $output
echo "#ifdef __cplusplus" >> $output
echo "# define EXPORTED_CONST extern const" >> $output
echo "#else" >> $output
echo "# define EXPORTED_CONST const" >> $output
echo "#endif" >> $output
echo "EXPORTED_CONST char *const xml_builtin[][2] = {" >> $output
for input; do
basename=`echo $input | sed 's,.*/,,'`

2
gdb/guile/guile.c
View File

@ -77,7 +77,7 @@ extern const struct extension_language_ops guile_extension_ops;
/* The main struct describing GDB's interface to the Guile
extension language. */
const struct extension_language_defn extension_language_guile =
EXPORTED_CONST struct extension_language_defn extension_language_guile =
{
EXT_LANG_GUILE,
"guile",