On 29/04/21 16:06 -0400, David Edelsohn wrote:
On Fri, Jan 8, 2021 at 1:37 PM Jonathan Wakely <jwak...@redhat.com> wrote:
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.
Hi, Jonathan
Polite ping.
Now that GCC 11.1 has been released, can this patch be applied to
libstdc++? As I replied at the time to Jakub's concerns, both Clang
(since 3.0.0) and ICC (since at least 16.0.0) have defined
__INT64_TYPE__ .
Pushed to trunk after testing on x86_64-linux and powerpc-aix.
commit 7ddcd26ebb60a8a4b57330442631115cabb6ec22
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Fri Apr 30 15:54:14 2021
libstdc++: Remove GLIBCXX_CHECK_INT64_T checks
This simplifies the definition of std::streamoff by using the predefined
__INT64_TYPE__ macro, instead of the _GLIBCXX_HAVE_INT64_T_LONG,
_GLIBCXX_HAVE_INT64_T_LONG_LONG and _GLIBCXX_HAVE_INT64_T macros defined
by configure.
By using the __INT64_TYPE__ macro (which all of GCC, Clang and Intel
define) we do not need to determine the type of int64_t in configure, we
can just use that type directly.
The background for the change was explained by David Edelsohn:
Currently the type of streamoff is determined at libstdc++ configure
time, chosen by the definitions of _GLIBCXX_HAVE_INT64_T_LONG and
_GLIBCXX_HAVE_INT64_T_LONG_LONG. For a multilib configuration, the
difference is encoded in the different multilib header file paths.
For "FAT" library targets that package 32 bit and 64 bit libraries
together, G++ also expects a single header file directory hierarchy,
causing an incorrect value for streamoff in some situations.
And in a subsequent mail:
Most of the libstdc++ headers are architecture-neutral, OS neutral and
ABI neutral. The differences are localized in bits/c++config.h. And
most of c++config.h is identical for 32 bit AIX and 64 bit AIX. The
only differences that matter are __int128 and __int64_t.
This change removes some of those differences. With the only uses of the
INT64_T configure macros removed, the configure checks themselves can
also be removed.
Co-authored-by: David Edelsohn <dje....@gmail.com>
libstdc++-v3/ChangeLog:
* acinclude.m4 (GLIBCXX_CHECK_INT64_T): Delete.
* config.h.in: Regenerate.
* configure: Regenerate.
* configure.ac: Do not use GLIBCXX_CHECK_INT64_T.
* include/bits/postypes.h: Remove include of <stdint.h> and
definition/undefinition of the __STDC_LIMIT_MACROS and
__STDC_CONSTANT_MACROS macros.
(streamoff): Use __INT64_TYPE__ if defined.
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 1c0a4c13052..7b78e148fbd 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..95dd9ce5da5 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 cb44cfe1396..52590ddd61b 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
