Re: [RFC] Another look at LFS vs filebuf::showmanyc

[Paolo Carlini <pcarlini at suse dot de>]

Paolo Carlini wrote:

> Nathan Myers wrote:
>
> > I agree.  I see little benefit to ever returning a value bigger than 
> > (say) 1M.
>
> Good, thanks. I'm already testing a patch.

Ok, just tested the below both on x86 and x86-64. Also verified that 4 
recent
glibcs (december 2003, january 2004, april 2004, june 2004) are ok wrt 
to the
fstat64 visibility issue. I'm beginning to think that maybe, last time I 
worked
on it, I did something wrong myself :( ...

Anyway, if nobody objects I'd like to apply the below to mainline real soon.

Thanks,
Paolo.

///////////////
2004-09-20  Paolo Carlini  <pcarlini@suse.de>

	PR libstdc++/12882 (cont)
	* acinclude.m4 (GLIBCXX_CHECK_LFS): Check for fstat64 too.
	* configure: Regenerate.
	* config/io/basic_file_stdio.cc (__basic_file<>::showmanyc): When
	_GLIBCXX_USE_LFS use fstat64 and lseek64, thus providing a non
	trivial showmanyc for large files too.

diff -urN libstdc++-v3-orig/acinclude.m4 libstdc++-v3/acinclude.m4
--- libstdc++-v3-orig/acinclude.m4	2004-08-02 22:28:11.000000000 +0200
+++ libstdc++-v3/acinclude.m4	2004-09-20 20:13:45.000000000 +0200
@@ -573,12 +573,15 @@
     AC_TRY_LINK(
       [#include <unistd.h>
        #include <stdio.h>
+       #include <sys/stat.h>
       ],
       [FILE* fp;
        fopen64("t", "w");
        fseeko64(fp, 0, SEEK_CUR);
        ftello64(fp);
-       lseek64(1, 0, SEEK_CUR);],	
+       lseek64(1, 0, SEEK_CUR);
+       struct stat64 buf;
+       fstat64(1, &buf);],
       [glibcxx_cv_LFS=yes],
       [glibcxx_cv_LFS=no])
   ])
diff -urN libstdc++-v3-orig/config/io/basic_file_stdio.cc libstdc++-v3/config/io/basic_file_stdio.cc
--- libstdc++-v3-orig/config/io/basic_file_stdio.cc	2004-09-16 18:04:21.000000000 +0200
+++ libstdc++-v3/config/io/basic_file_stdio.cc	2004-09-20 19:52:05.000000000 +0200
@@ -68,7 +68,7 @@
 # endif
 #endif
 
-#include <limits> // For <off_t>::max() and min()
+#include <limits> // For <off_t>::max() and min() and <streamsize>::max()
 
 namespace __gnu_internal
 {
@@ -315,8 +315,8 @@
 #ifdef _GLIBCXX_USE_LFS
     return lseek64(this->fd(), __off, __way);
 #else
-    if (__off > std::numeric_limits<off_t>::max()
-	|| __off < std::numeric_limits<off_t>::min())
+    if (__off > numeric_limits<off_t>::max()
+	|| __off < numeric_limits<off_t>::min())
       return -1L;
     return lseek(this->fd(), __off, __way);
 #endif
@@ -352,10 +352,21 @@
 
 #if defined(_GLIBCXX_HAVE_S_ISREG) || defined(_GLIBCXX_HAVE_S_IFREG)
     // Regular files.
+#ifdef _GLIBCXX_USE_LFS
+    struct stat64 __buffer;
+    const int __err = fstat64(this->fd(), &__buffer);
+    if (!__err && _GLIBCXX_ISREG(__buffer.st_mode))
+      {
+	const streamoff __off = __buffer.st_size - lseek64(this->fd(), 0,
+							   ios_base::cur);
+	return std::min(__off, streamoff(numeric_limits<streamsize>::max()));
+      }
+#else
     struct stat __buffer;
-    int __ret = fstat(this->fd(), &__buffer);
-    if (!__ret && _GLIBCXX_ISREG(__buffer.st_mode))
-	return __buffer.st_size - lseek(this->fd(), 0, ios_base::cur);
+    const int __err = fstat(this->fd(), &__buffer);
+    if (!__err && _GLIBCXX_ISREG(__buffer.st_mode))
+      return __buffer.st_size - lseek(this->fd(), 0, ios_base::cur);
+#endif
 #endif
     return 0;
   }