This shows up as an assertion failure when sprintf is called with
a specifier like "%.8g" and libquadmath is linked in:

Fatal glibc error: printf_buffer_as_file.c:31
  (__printf_buffer_as_file_commit): assertion failed:
  file->stream._IO_write_ptr <= file->next->write_end

Fix this by detecting pointer wraparound in __vsprintf_internal
and saturate the addition to the end of the address space instead.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

I used these shell commands:

../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")

and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.

I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah.  I don't
know why I run into these diagnostics whereas others evidently do not.

remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines

I used these shell commands:

../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")

and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master

Also, change sources.redhat.com to sourceware.org.
This patch was automatically generated by running the following shell
script, which uses GNU sed, and which avoids modifying files imported
from upstream:

sed -ri '
  s,(http|ftp)(://(.*\.)?(gnu|fsf|sourceware)\.org($|[^.]|\.[^a-z])),https\2,g
  s,(http|ftp)(://(.*\.)?)sources\.redhat\.com($|[^.]|\.[^a-z]),https\2sourceware.org\4,g
' \
  $(find $(git ls-files) -prune -type f \
      ! -name '*.po' \
      ! -name 'ChangeLog*' \
      ! -path COPYING ! -path COPYING.LIB \
      ! -path manual/fdl-1.3.texi ! -path manual/lgpl-2.1.texi \
      ! -path manual/texinfo.tex ! -path scripts/config.guess \
      ! -path scripts/config.sub ! -path scripts/install-sh \
      ! -path scripts/mkinstalldirs ! -path scripts/move-if-change \
      ! -path INSTALL ! -path  locale/programs/charmap-kw.h \
      ! -path po/libc.pot ! -path sysdeps/gnu/errlist.c \
      ! '(' -name configure \
            -execdir test -f configure.ac -o -f configure.in ';' ')' \
      ! '(' -name preconfigure \
            -execdir test -f preconfigure.ac ';' ')' \
      -print)

and then by running 'make dist-prepare' to regenerate files built
from the altered files, and then executing the following to cleanup:

  chmod a+x sysdeps/unix/sysv/linux/riscv/configure
  # Omit irrelevant whitespace and comment-only changes,
  # perhaps from a slightly-different Autoconf version.
  git checkout -f \
    sysdeps/csky/configure \
    sysdeps/hppa/configure \
    sysdeps/riscv/configure \
    sysdeps/unix/sysv/linux/csky/configure
  # Omit changes that caused a pre-commit check to fail like this:
  # remote: *** error: sysdeps/powerpc/powerpc64/ppc-mcount.S: trailing lines
  git checkout -f \
    sysdeps/powerpc/powerpc64/ppc-mcount.S \
    sysdeps/unix/sysv/linux/s390/s390-64/syscall.S
  # Omit change that caused a pre-commit check to fail like this:
  # remote: *** error: sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S: last line does not end in newline
  git checkout -f sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S

According to ISO C99, passing the same buffer as source and destination
to sprintf, snprintf, vsprintf, or vsnprintf has undefined behavior.
Until the commit

  commit 4e2f43f842ef5e253cc23383645adbaa03cedb86
  Author: Zack Weinberg <zackw@panix.com>
  Date:   Wed Mar 7 14:32:03 2018 -0500

      Use PRINTF_FORTIFY instead of _IO_FLAGS2_FORTIFY (bug 11319)

a call to sprintf or vsprintf with overlapping buffers, for instance
vsprintf (buf, "%sTEXT", buf), would append `TEXT' into buf, while a
call to snprintf or vsnprintf would override the contents of buf.
After the aforementioned commit, the behavior of sprintf and vsprintf
changed (so that they also override the contents of buf).

This patch reverts this behavioral change, because it will likely break
applications that rely on the previous behavior, even though it is
undefined by ISO C.  As noted by Szabolcs Nagy, this is used in SPEC2017
507.cactuBSSN_r/src/PUGH/PughUtils.c:

  sprintf(mess,"  Size:");
  for (i=0;i<dim+1;i++)
  {
      sprintf(mess,"%s %d",mess,pughGH->GFExtras[dim]->nsize[i]);
  }

More important to notice is the fact that the overwriting of the
destination buffer is not the only behavior affected by the refactoring.
Before the refactoring, sprintf and vsprintf would use _IO_str_jumps,
whereas __sprintf_chk and __vsprintf_chk would use _IO_str_chk_jumps.
After the refactoring, all use _IO_str_chk_jumps, which would make
sprintf and vsprintf report buffer overflows and terminate the program.
This patch also reverts this behavior, by installing the appropriate
jump table for each *sprintf functions.

Apart from reverting the changes, this patch adds a test case that has
the old behavior hardcoded, so that regressions are noticed if something
else unintentionally changes the behavior.

Tested for powerpc64le.