[glibc/vineet/arc-port-latest] Fix stringop-overflow errors from gcc 10 in iconv.

[Vineet Gupta <vgupta@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=08538f360f14dbe2e3b04a30148e342f248d9de5

commit 08538f360f14dbe2e3b04a30148e342f248d9de5
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Tue Jun 16 14:24:20 2020 +0200

    Fix stringop-overflow errors from gcc 10 in iconv.
    
    On s390x, I've recognize various -Werror=stringop-overflow messages
    in iconv/loop.c and iconv/skeleton.c if build with gcc10 -O3.
    
    With this commit gcc knows the size and do not raise those errors anymore.

Diff:
---
 iconv/loop.c     | 14 ++++++++------
 iconv/skeleton.c |  8 +++++---
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/iconv/loop.c b/iconv/loop.c
index 9f7570d591..b032fcd9ac 100644
--- a/iconv/loop.c
+++ b/iconv/loop.c
@@ -420,8 +420,10 @@ SINGLE(LOOPFCT) (struct __gconv_step *step,
 #  else
       /* We don't have enough input for another complete input
 	 character.  */
-      while (inptr < inend)
-	state->__value.__wchb[inlen++] = *inptr++;
+      size_t inlen_after = inlen + (inend - inptr);
+      assert (inlen_after <= sizeof (state->__value.__wchb));
+      for (; inlen < inlen_after; inlen++)
+	state->__value.__wchb[inlen] = *inptr++;
 #  endif
 
       return __GCONV_INCOMPLETE_INPUT;
@@ -483,11 +485,11 @@ SINGLE(LOOPFCT) (struct __gconv_step *step,
       /* We don't have enough input for another complete input
 	 character.  */
       assert (inend - inptr > (state->__count & ~7));
-      assert (inend - inptr <= sizeof (state->__value));
+      assert (inend - inptr <= sizeof (state->__value.__wchb));
       state->__count = (state->__count & ~7) | (inend - inptr);
-      inlen = 0;
-      while (inptr < inend)
-	state->__value.__wchb[inlen++] = *inptr++;
+      for (inlen = 0; inlen < inend - inptr; inlen++)
+	state->__value.__wchb[inlen] = inptr[inlen];
+      inptr = inend;
 #  endif
     }
 
diff --git a/iconv/skeleton.c b/iconv/skeleton.c
index 1dc642e2fc..1a38b51a5a 100644
--- a/iconv/skeleton.c
+++ b/iconv/skeleton.c
@@ -795,11 +795,13 @@ FUNCTION_NAME (struct __gconv_step *step, struct __gconv_step_data *data,
 # else
 	  /* Make sure the remaining bytes fit into the state objects
 	     buffer.  */
-	  assert (inend - *inptrp < 4);
+	  size_t cnt_after = inend - *inptrp;
+	  assert (cnt_after <= sizeof (data->__statep->__value.__wchb));
 
 	  size_t cnt;
-	  for (cnt = 0; *inptrp < inend; ++cnt)
-	    data->__statep->__value.__wchb[cnt] = *(*inptrp)++;
+	  for (cnt = 0; cnt < cnt_after; ++cnt)
+	    data->__statep->__value.__wchb[cnt] = (*inptrp)[cnt];
+	  *inptrp = inend;
 	  data->__statep->__count &= ~7;
 	  data->__statep->__count |= cnt;
 # endif