PR middle-end/94647 - bogus -Warray-bounds on strncpy into a larger member array from a smaller array

gcc/ChangeLog:

	PR middle-end/94647
	* gimple-ssa-warn-restrict.c (builtin_access::builtin_access): Correct
	the computation of the lower bound of the source access size.
	(builtin_access::generic_overlap): Remove a hack for setting ranges
	of overlap offsets.

gcc/testsuite/ChangeLog:

	PR middle-end/94647
	* c-c++-common/Warray-bounds-2.c: Adjust a test case and add a new one.
	* c-c++-common/Warray-bounds-3.c: Add tests for missing warnings.
	* c-c++-common/Wrestrict.c: Invert bounds in printed ranges.
	* gcc.dg/Warray-bounds-59.c: New test.
	* gcc.dg/Wrestrict-10.c: Add a missing warning.
	* gcc.dg/Wrestrict-5.c: Adjust text of expected warning.
	* gcc.dg/Wrestrict-6.c: Expect to see a range of overlap offsets.

1 files changed, 9 insertions, 31 deletions

diff --git a/gcc/gimple-ssa-warn-restrict.c b/gcc/gimple-ssa-warn-restrict.c
index a6a96353a8c..19d2ec09aa5 100644
--- a/gcc/gimple-ssa-warn-restrict.c
+++ b/gcc/gimple-ssa-warn-restrict.c
@@ -831,8 +831,8 @@ builtin_access::builtin_access (gimple *call, builtin_memref &dst,
     }
   else if (srcref->sizrange[0] == 0 && srcref->sizrange[1] == maxobjsize)
     {
-      /* When the source size is unknown set it to the size of
-	 the destination.  */
+      /* When the size of the source access is unknown set it to the size
+	 of the destination first and adjust it later if necessary.  */
       srcref->sizrange[0] = dstref->sizrange[0];
       srcref->sizrange[1] = dstref->sizrange[1];
 
@@ -842,15 +842,11 @@ builtin_access::builtin_access (gimple *call, builtin_memref &dst,
 	    {
 	      /* Read access by strncpy is constrained by the third
 		 argument but except for a zero bound is at least one.  */
-	      offset_int size = wi::umax (srcref->basesize, 1);
-	      offset_int bound = wi::umin (size, bounds[0]);
-	      if (bound < srcref->sizrange[0])
-		srcref->sizrange[0] = bound;
-	      bound = wi::umin (srcref->basesize, bounds[1]);
+	      srcref->sizrange[0] = bounds[1] > 0 ? 1 : 0;
+	      offset_int bound = wi::umin (srcref->basesize, bounds[1]);
 	      if (bound < srcref->sizrange[1])
 		srcref->sizrange[1] = bound;
 	    }
-
 	  /* For string functions, adjust the size range of the source
 	     reference by the inverse boundaries of the offset (because
 	     the higher the offset into the string the shorter its
@@ -859,7 +855,7 @@ builtin_access::builtin_access (gimple *call, builtin_memref &dst,
 	      && srcref->offrange[1] < srcref->sizrange[0])
 	    srcref->sizrange[0] -= srcref->offrange[1];
 	  else
-	    srcref->sizrange[0] = 0;
+	    srcref->sizrange[0] = 1;
 
 	  if (srcref->offrange[0] > 0)
 	    {
@@ -1060,16 +1056,8 @@ builtin_access::generic_overlap ()
   ovloff[0] = HOST_WIDE_INT_MAX;
   ovloff[1] = HOST_WIDE_INT_MIN;
 
-  /* Adjustment to the lower bound of the offset of the overlap to
-     account for a subset of unbounded string calls where the size
-     of the destination string depends on the length of the source
-     which in turn depends on the offset into it.  */
-  bool sub1;
-
   if (stxcpy_p)
     {
-      sub1 = acs.dstoff[0] <= acs.srcoff[0];
-
       /* Iterate over the extreme locations (on the horizontal axis formed
 	 by their offsets) and sizes of two regions and find their smallest
 	 and largest overlap and the corresponding offsets.  */
@@ -1102,11 +1090,9 @@ builtin_access::generic_overlap ()
     }
   else
     {
-      sub1 = !depends_p;
-
       /* Iterate over the extreme locations (on the horizontal axis
-	 formed by their offsets) and sizes of two regions and find
-	 their smallest and largest overlap and the corresponding
+	 formed by their offsets) and sizes of the two regions and
+	 find their smallest and largest overlap and the corresponding
 	 offsets.  */
 
       for (unsigned io = 0; io != 2; ++io)
@@ -1119,15 +1105,6 @@ builtin_access::generic_overlap ()
 	    for (unsigned jo = 0; jo != 2; ++jo)
 	      for (unsigned js = 0; js != 2; ++js)
 		{
-		  if (depends_p)
-		    {
-		      /* For st{p,r}ncpy the size of the source sequence
-			 depends on the offset into it.  */
-		      if (js)
-			break;
-		      js = !jo;
-		    }
-
 		  const offset_int b[2] = {
 		    acs.srcoff[jo], acs.srcoff[jo] + acs.srcsiz[js]
 		  };
@@ -1154,8 +1131,9 @@ builtin_access::generic_overlap ()
   ovlsiz[0] = siz[0].to_shwi ();
   ovlsiz[1] = siz[1].to_shwi ();
 
+  /* Adjust the overlap offset range to reflect the overlap size range.  */
   if (ovlsiz[0] == 0 && ovlsiz[1] > 1)
-    ovloff[0] = ovloff[1] + ovlsiz[1] - 1 - sub1;
+    ovloff[1] = ovloff[0] + ovlsiz[1] - 1;
 
   return true;
 }