Avoid stpncpy

It’s not worth the porting hassle, and as the glibc manual says,
“this function is generally a poor choice for processing strings”.
* admin/merge-gnulib (GNULIB_MODULES): Remove stpncpy.
* exec/configure.ac: Do not check for stpncpy.
* exec/exec.c (rpl_stpncpy, stpncpy): Remove this replacement.
(exec_0): Properly clear buffer1.  Use memcpy instead of
stpncpy to add the trailing name.  This code is clearly
still suboptimal but efficiency is not that important here
and I tried to minimize the change.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.

7 files changed, 8 insertions, 297 deletions

diff --git a/admin/merge-gnulib b/admin/merge-gnulib
index f64c0670bcf..2a713beb01a 100755
--- a/admin/merge-gnulib
+++ b/admin/merge-gnulib
@@ -45,7 +45,7 @@ GNULIB_MODULES='
   pathmax pipe2 pselect pthread_sigmask
   qcopy-acl readlink readlinkat regex
   sig2str sigdescr_np socklen stat-time std-gnu11 stdbool stdckdint stddef stdio
-  stpcpy stpncpy strnlen strnlen strtoimax symlink sys_stat sys_time
+  stpcpy strnlen strnlen strtoimax symlink sys_stat sys_time
   tempname time-h time_r time_rz timegm timer-time timespec-add timespec-sub
   update-copyright unlocked-io utimensat
   vla warnings year2038
diff --git a/exec/configure.ac b/exec/configure.ac
index e78d8ebea90..180c200d13d 100644
--- a/exec/configure.ac
+++ b/exec/configure.ac
@@ -62,8 +62,8 @@ AC_TYPE_SSIZE_T
 AC_TYPE_PID_T
 
 AC_HEADER_STDBOOL
-AC_CHECK_FUNCS([getpagesize stpcpy stpncpy])
-AC_CHECK_DECLS([stpcpy, stpncpy])
+AC_CHECK_FUNCS([getpagesize stpcpy])
+AC_CHECK_DECLS([stpcpy])
 AC_CHECK_FUNC([process_vm_readv],
   [AC_CHECK_FUNC([process_vm_writev],
     [AC_CHECK_DECL([process_vm_readv],
diff --git a/exec/exec.c b/exec/exec.c
index 935c94a59af..dae05755675 100644
--- a/exec/exec.c
+++ b/exec/exec.c
@@ -66,74 +66,6 @@ rpl_stpcpy (char *dest, const char *src)
 #define stpcpy rpl_stpcpy
 #endif /* !defined HAVE_STPCPY || !defined HAVE_DECL_STPCPY */
 
-#if !defined HAVE_STPNCPY || !defined HAVE_DECL_STPNCPY
-
-/* Copy no more than N bytes of SRC to DST, returning a pointer past
-   the last non-NUL byte written into DST.  */
-
-static char *
-rpl_stpncpy (char *dest, const char *src, size_t n)
-{
-  char c, *s;
-  size_t n4;
-
-  s = dest;
-
-  if (n >= 4)
-    {
-      n4 = n >> 2;
-
-      for (;;)
-        {
-          c = *src++;
-          *dest++ = c;
-          if (c == '\0')
-            break;
-          c = *src++;
-          *dest++ = c;
-          if (c == '\0')
-            break;
-          c = *src++;
-          *dest++ = c;
-          if (c == '\0')
-            break;
-          c = *src++;
-          *dest++ = c;
-          if (c == '\0')
-            break;
-          if (--n4 == 0)
-            goto last_chars;
-        }
-      n -= dest - s;
-      goto zero_fill;
-    }
-
- last_chars:
-  n &= 3;
-  if (n == 0)
-    return dest;
-
-  for (;;)
-    {
-      c = *src++;
-      --n;
-      *dest++ = c;
-      if (c == '\0')
-        break;
-      if (n == 0)
-        return dest;
-    }
-
- zero_fill:
-  while (n-- > 0)
-    dest[n] = '\0';
-
-  return dest - 1;
-}
-
-#define stpncpy rpl_stpncpy
-#endif /* !defined HAVE_STPNCPY || !defined HAVE_DECL_STPNCPY */
-
 
 
 /* Executable reading functions.
@@ -1005,13 +937,14 @@ exec_0 (char *name, struct exec_tracee *tracee,
   else
     {
       /* If name is not absolute, then make it relative to TRACEE's
-         cwd.  Use stpcpy, as sprintf is not reentrant.  */
+         cwd.  Do not use sprintf at it is not reentrant and it
+         mishandles results longer than INT_MAX.  */
 
       if (name[0] && name[0] != '/')
         {
-          /* Clear `buffer'.  */
+          /* Clear both buffers.  */
           memset (buffer, 0, sizeof buffer);
-          memset (buffer1, 0, sizeof buffer);
+          memset (buffer1, 0, sizeof buffer1);
 
           /* Copy over /proc, the PID, and /cwd/.  */
           rewrite = stpcpy (buffer, "/proc/");
@@ -1042,7 +975,7 @@ exec_0 (char *name, struct exec_tracee *tracee,
 
           rewrite = buffer1 + link_size;
           remaining = buffer1 + sizeof buffer1 - rewrite - 1;
-          rewrite = stpncpy (rewrite, name, remaining);
+          memcpy (rewrite, name, strnlen (name, remaining));
 
           /* Replace name with buffer1.  */
 #ifndef REENTRANT
diff --git a/lib/gnulib.mk.in b/lib/gnulib.mk.in
index 78ecb544c6e..785bdc70c5c 100644
--- a/lib/gnulib.mk.in
+++ b/lib/gnulib.mk.in
@@ -157,7 +157,6 @@
 #  stddef \
 #  stdio \
 #  stpcpy \
-#  stpncpy \
 #  strnlen \
 #  strtoimax \
 #  symlink \
@@ -336,7 +335,6 @@ GL_COND_OBJ_SIGDESCR_NP_CONDITION = @GL_COND_OBJ_SIGDESCR_NP_CONDITION@
 GL_COND_OBJ_STDIO_READ_CONDITION = @GL_COND_OBJ_STDIO_READ_CONDITION@
 GL_COND_OBJ_STDIO_WRITE_CONDITION = @GL_COND_OBJ_STDIO_WRITE_CONDITION@
 GL_COND_OBJ_STPCPY_CONDITION = @GL_COND_OBJ_STPCPY_CONDITION@
-GL_COND_OBJ_STPNCPY_CONDITION = @GL_COND_OBJ_STPNCPY_CONDITION@
 GL_COND_OBJ_STRNLEN_CONDITION = @GL_COND_OBJ_STRNLEN_CONDITION@
 GL_COND_OBJ_STRTOIMAX_CONDITION = @GL_COND_OBJ_STRTOIMAX_CONDITION@
 GL_COND_OBJ_STRTOLL_CONDITION = @GL_COND_OBJ_STRTOLL_CONDITION@
@@ -3454,16 +3452,6 @@ endif
 endif
 ## end   gnulib module stpcpy
 
-## begin gnulib module stpncpy
-ifeq (,$(OMIT_GNULIB_MODULE_stpncpy))
-
-ifneq (,$(GL_COND_OBJ_STPNCPY_CONDITION))
-libgnu_a_SOURCES += stpncpy.c
-endif
-
-endif
-## end   gnulib module stpncpy
-
 ## begin gnulib module string
 ifeq (,$(OMIT_GNULIB_MODULE_string))
 
diff --git a/lib/stpncpy.c b/lib/stpncpy.c
deleted file mode 100644
index d1422a927df..00000000000
--- a/lib/stpncpy.c
+++ /dev/null
@@ -1,92 +0,0 @@
-/* Copyright (C) 1993, 1995-1997, 2002-2003, 2005-2007, 2009-2023 Free Software
- * Foundation, Inc.
-
-   NOTE: The canonical source of this file is maintained with the GNU C Library.
-   Bugs can be reported to bug-glibc@gnu.org.
-
-   This file is free software: you can redistribute it and/or modify
-   it under the terms of the GNU Lesser General Public License as
-   published by the Free Software Foundation; either version 2.1 of the
-   License, or (at your option) any later version.
-
-   This file is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-   GNU Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public License
-   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
-
-/* This is almost copied from strncpy.c, written by Torbjorn Granlund.  */
-
-#include <config.h>
-
-/* Specification.  */
-#include <string.h>
-
-#ifndef weak_alias
-# define __stpncpy stpncpy
-#endif
-
-/* Copy no more than N bytes of SRC to DST, returning a pointer past the
-   last non-NUL byte written into DST.  */
-char *
-(__stpncpy) (char *dest, const char *src, size_t n)
-{
-  char c;
-  char *s = dest;
-
-  if (n >= 4)
-    {
-      size_t n4 = n >> 2;
-
-      for (;;)
-        {
-          c = *src++;
-          *dest++ = c;
-          if (c == '\0')
-            break;
-          c = *src++;
-          *dest++ = c;
-          if (c == '\0')
-            break;
-          c = *src++;
-          *dest++ = c;
-          if (c == '\0')
-            break;
-          c = *src++;
-          *dest++ = c;
-          if (c == '\0')
-            break;
-          if (--n4 == 0)
-            goto last_chars;
-        }
-      n -= dest - s;
-      goto zero_fill;
-    }
-
- last_chars:
-  n &= 3;
-  if (n == 0)
-    return dest;
-
-  for (;;)
-    {
-      c = *src++;
-      --n;
-      *dest++ = c;
-      if (c == '\0')
-        break;
-      if (n == 0)
-        return dest;
-    }
-
- zero_fill:
-  while (n-- > 0)
-    dest[n] = '\0';
-
-  return dest - 1;
-}
-#ifdef weak_alias
-weak_alias (__stpncpy, stpncpy)
-#endif
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 72adcf90d5e..3382e9bc241 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -181,7 +181,6 @@ AC_DEFUN([gl_EARLY],
   gl_STDIO_H_EARLY
   # Code from module stdlib:
   # Code from module stpcpy:
-  # Code from module stpncpy:
   # Code from module string:
   # Code from module strnlen:
   # Code from module strtoimax:
@@ -567,13 +566,6 @@ AC_DEFUN([gl_INIT],
     gl_PREREQ_STPCPY
   ])
   gl_STRING_MODULE_INDICATOR([stpcpy])
-  gl_FUNC_STPNCPY
-  gl_CONDITIONAL([GL_COND_OBJ_STPNCPY],
-                 [test $HAVE_STPNCPY = 0 || test $REPLACE_STPNCPY = 1])
-  AM_COND_IF([GL_COND_OBJ_STPNCPY], [
-    gl_PREREQ_STPNCPY
-  ])
-  gl_STRING_MODULE_INDICATOR([stpncpy])
   gl_STRING_H
   gl_STRING_H_REQUIRE_DEFAULTS
   AC_PROG_MKDIR_P
@@ -1422,7 +1414,6 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/stdio.in.h
   lib/stdlib.in.h
   lib/stpcpy.c
-  lib/stpncpy.c
   lib/str-two-way.h
   lib/strftime.h
   lib/string.in.h
@@ -1569,7 +1560,6 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/stdio_h.m4
   m4/stdlib_h.m4
   m4/stpcpy.m4
-  m4/stpncpy.m4
   m4/string_h.m4
   m4/strnlen.m4
   m4/strtoimax.m4
diff --git a/m4/stpncpy.m4 b/m4/stpncpy.m4
deleted file mode 100644
index 073607004be..00000000000
--- a/m4/stpncpy.m4
+++ /dev/null
@@ -1,108 +0,0 @@
-# stpncpy.m4 serial 22
-dnl Copyright (C) 2002-2003, 2005-2007, 2009-2023 Free Software Foundation,
-dnl Inc.
-dnl This file is free software; the Free Software Foundation
-dnl gives unlimited permission to copy and/or distribute it,
-dnl with or without modifications, as long as this notice is preserved.
-
-AC_DEFUN([gl_FUNC_STPNCPY],
-[
-  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
-
-  dnl Persuade glibc <string.h> to declare stpncpy().
-  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
-
-  dnl The stpncpy() declaration in lib/string.in.h uses 'restrict'.
-  AC_REQUIRE([AC_C_RESTRICT])
-
-  AC_REQUIRE([gl_STRING_H_DEFAULTS])
-
-  dnl Both glibc and AIX (4.3.3, 5.1) have an stpncpy() function
-  dnl declared in <string.h>. Its side effects are the same as those
-  dnl of strncpy():
-  dnl      stpncpy (dest, src, n)
-  dnl overwrites dest[0..n-1], min(strlen(src),n) bytes coming from src,
-  dnl and the remaining bytes being NULs.  However, the return value is
-  dnl   in glibc:   dest + min(strlen(src),n)
-  dnl   in AIX:     dest + max(0,n-1)
-  dnl Only the glibc return value is useful in practice.
-
-  AC_CHECK_DECLS_ONCE([stpncpy])
-  gl_CHECK_FUNCS_ANDROID([stpncpy], [[#include <string.h>]])
-  if test $ac_cv_func_stpncpy = yes; then
-    AC_CACHE_CHECK([for working stpncpy], [gl_cv_func_stpncpy], [
-      AC_RUN_IFELSE(
-        [AC_LANG_SOURCE([[
-#include <stdlib.h>
-#include <string.h> /* for strcpy */
-/* The stpncpy prototype is missing in <string.h> on AIX 4.  */
-#if !HAVE_DECL_STPNCPY
-extern
-# ifdef __cplusplus
-"C"
-# endif
-char *stpncpy (char *dest, const char *src, size_t n);
-#endif
-int main ()
-{
-  int result = 0;
-  const char *src = "Hello";
-  char dest[10];
-  /* AIX 4.3.3 and AIX 5.1 stpncpy() returns dest+1 here.  */
-  {
-    strcpy (dest, "\377\377\377\377\377\377");
-    if (stpncpy (dest, src, 2) != dest + 2)
-      result |= 1;
-  }
-  /* AIX 4.3.3 and AIX 5.1 stpncpy() returns dest+4 here.  */
-  {
-    strcpy (dest, "\377\377\377\377\377\377");
-    if (stpncpy (dest, src, 5) != dest + 5)
-      result |= 2;
-  }
-  /* AIX 4.3.3 and AIX 5.1 stpncpy() returns dest+6 here.  */
-  {
-    strcpy (dest, "\377\377\377\377\377\377");
-    if (stpncpy (dest, src, 7) != dest + 5)
-      result |= 4;
-  }
-  return result;
-}
-]])],
-        [gl_cv_func_stpncpy=yes],
-        [gl_cv_func_stpncpy=no],
-        [dnl Guess yes on glibc systems and musl systems.
-         AC_EGREP_CPP([Thanks for using GNU], [
-#include <features.h>
-#ifdef __GNU_LIBRARY__
-  Thanks for using GNU
-#endif
-],         [gl_cv_func_stpncpy="guessing yes"],
-           [case "$host_os" in
-              *-musl* | midipix*) gl_cv_func_stpncpy="guessing yes" ;;
-              *)                  gl_cv_func_stpncpy="$gl_cross_guess_normal" ;;
-            esac
-           ])
-        ])
-    ])
-    case "$gl_cv_func_stpncpy" in
-      *yes)
-        AC_DEFINE([HAVE_STPNCPY], [1],
-          [Define if you have the stpncpy() function and it works.])
-        ;;
-      *)
-        REPLACE_STPNCPY=1
-        ;;
-    esac
-  else
-    HAVE_STPNCPY=0
-    case "$gl_cv_onwards_func_stpncpy" in
-      future*) REPLACE_STPNCPY=1 ;;
-    esac
-  fi
-])
-
-# Prerequisites of lib/stpncpy.c.
-AC_DEFUN([gl_PREREQ_STPNCPY], [
-  :
-])