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.

2 files changed, 13 insertions, 9 deletions

diff --git a/iconv/loop.c b/iconv/loop.c
index 9f7570d..b032fcd 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 1dc642e..1a38b51 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