On 06/01/21 19:41 -0500, David Edelsohn wrote:
Thanks for clarifying the issue.
As you implicitly point out, GCC knows the type of INT64 and defines
the macro __INT64_TYPE__ . The revised code can use that directly,
such as:
#if defined(_GLIBCXX_HAVE_INT64_T_LONG) \
|| defined(_GLIBCXX_HAVE_INT64_T_LONG_LONG)
typedef __INT64_TYPE__ streamoff;
#elif defined(_GLIBCXX_HAVE_INT64_T)
typedef int64_t streamoff;
#else
typedef long long streamoff;
#endif
Are there any additional issues not addressed by that approach, other
than possible further simplification?
That avoids the ABI break that Jakub pointed out. But I think we can
simplify it further, as in the attached patch.
This uses __INT64_TYPE__ if that's defined, and long long otherwise. I
think that should be equivalent in all practical cases (I can imagine
some strange target where __INT64_TYPE__ is defined by the compiler,
but int64_t isn't defined when the configure checks look for it, and
so the current code would use long long and with my patch would use
__INT64_TYPE__ which could be long ... but I think in practice that's
unlikely. It was probably more likely in older releases where the
configure test would have been done with -std=gnu++98 and so int64_t
might not have been declared by libc's <stdint.h>, but if that was the
case then any ABI break it caused happened years ago.
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index e4175ea3e64..f13c5d2467f 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -474,63 +474,6 @@ AC_DEFUN([GLIBCXX_CHECK_WRITEV], [
])
-dnl
-dnl Check whether int64_t is available in <stdint.h>, and define HAVE_INT64_T.
-dnl Also check whether int64_t is actually a typedef to long or long long.
-dnl
-AC_DEFUN([GLIBCXX_CHECK_INT64_T], [
-
- AC_LANG_SAVE
- AC_LANG_CPLUSPLUS
-
- AC_MSG_CHECKING([for int64_t])
- AC_CACHE_VAL(glibcxx_cv_INT64_T, [
- AC_TRY_COMPILE(
- [#include <stdint.h>],
- [int64_t var;],
- [glibcxx_cv_INT64_T=yes],
- [glibcxx_cv_INT64_T=no])
- ])
-
- if test $glibcxx_cv_INT64_T = yes; then
- AC_DEFINE(HAVE_INT64_T, 1, [Define if int64_t is available in <stdint.h>.])
- AC_MSG_RESULT($glibcxx_cv_INT64_T)
-
- AC_MSG_CHECKING([for int64_t as long])
- AC_CACHE_VAL(glibcxx_cv_int64_t_long, [
- AC_TRY_COMPILE(
- [#include <stdint.h>
- template<typename, typename> struct same { enum { value = -1 }; };
- template<typename Tp> struct same<Tp, Tp> { enum { value = 1 }; };
- int array[same<int64_t, long>::value];], [],
- [glibcxx_cv_int64_t_long=yes], [glibcxx_cv_int64_t_long=no])
- ])
-
- if test $glibcxx_cv_int64_t_long = yes; then
- AC_DEFINE(HAVE_INT64_T_LONG, 1, [Define if int64_t is a long.])
- AC_MSG_RESULT($glibcxx_cv_int64_t_long)
- fi
-
- AC_MSG_CHECKING([for int64_t as long long])
- AC_CACHE_VAL(glibcxx_cv_int64_t_long_long, [
- AC_TRY_COMPILE(
- [#include <stdint.h>
- template<typename, typename> struct same { enum { value = -1 }; };
- template<typename Tp> struct same<Tp, Tp> { enum { value = 1 }; };
- int array[same<int64_t, long long>::value];], [],
- [glibcxx_cv_int64_t_long_long=yes], [glibcxx_cv_int64_t_long_long=no])
- ])
-
- if test $glibcxx_cv_int64_t_long_long = yes; then
- AC_DEFINE(HAVE_INT64_T_LONG_LONG, 1, [Define if int64_t is a long long.])
- AC_MSG_RESULT($glibcxx_cv_int64_t_long_long)
- fi
- fi
-
- AC_LANG_RESTORE
-])
-
-
dnl
dnl Check whether LFS support is available.
dnl
diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
index 3c799be82b1..a816ff79d16 100644
--- a/libstdc++-v3/configure.ac
+++ b/libstdc++-v3/configure.ac
@@ -185,9 +185,6 @@ GLIBCXX_CHECK_STDIO_PROTO
GLIBCXX_CHECK_MATH11_PROTO
GLIBCXX_CHECK_UCHAR_H
-# For the streamoff typedef.
-GLIBCXX_CHECK_INT64_T
-
# For LFS support.
GLIBCXX_CHECK_LFS
diff --git a/libstdc++-v3/include/bits/postypes.h b/libstdc++-v3/include/bits/postypes.h
index 718ff44628c..d2fbfc35dee 100644
--- a/libstdc++-v3/include/bits/postypes.h
+++ b/libstdc++-v3/include/bits/postypes.h
@@ -39,32 +39,6 @@
#include <cwchar> // For mbstate_t
-// XXX If <stdint.h> is really needed, make sure to define the macros
-// before including it, in order not to break <tr1/cstdint> (and <cstdint>
-// in C++11). Reconsider all this as soon as possible...
-#if (defined(_GLIBCXX_HAVE_INT64_T) && !defined(_GLIBCXX_HAVE_INT64_T_LONG) \
- && !defined(_GLIBCXX_HAVE_INT64_T_LONG_LONG))
-
-#ifndef __STDC_LIMIT_MACROS
-# define _UNDEF__STDC_LIMIT_MACROS
-# define __STDC_LIMIT_MACROS
-#endif
-#ifndef __STDC_CONSTANT_MACROS
-# define _UNDEF__STDC_CONSTANT_MACROS
-# define __STDC_CONSTANT_MACROS
-#endif
-#include <stdint.h> // For int64_t
-#ifdef _UNDEF__STDC_LIMIT_MACROS
-# undef __STDC_LIMIT_MACROS
-# undef _UNDEF__STDC_LIMIT_MACROS
-#endif
-#ifdef _UNDEF__STDC_CONSTANT_MACROS
-# undef __STDC_CONSTANT_MACROS
-# undef _UNDEF__STDC_CONSTANT_MACROS
-#endif
-
-#endif
-
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -84,12 +58,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* Note: In versions of GCC up to and including GCC 3.3, streamoff
* was typedef long.
*/
-#ifdef _GLIBCXX_HAVE_INT64_T_LONG
- typedef long streamoff;
-#elif defined(_GLIBCXX_HAVE_INT64_T_LONG_LONG)
- typedef long long streamoff;
-#elif defined(_GLIBCXX_HAVE_INT64_T)
- typedef int64_t streamoff;
+#ifdef __INT64_TYPE__
+ typedef __INT64_TYPE__ streamoff;
#else
typedef long long streamoff;
#endif
