PR tree-optimization/83698 - bogus offset in -Wrestrict messages for strcat of unknown strings

gcc/ChangeLog:

	PR tree-optimization/83698
	* gimple-ssa-warn-restrict.c (builtin_memref::builtin_memref): For
	arrays constrain the offset range to their bounds.
	(builtin_access::strcat_overlap): Adjust the bounds of overlap offset.
	(builtin_access::overlap): Avoid setting the size of overlap if it's
	already been set.
	(maybe_diag_overlap): Also consider arrays when deciding what values
	of offsets to include in diagnostics.

gcc/testsuite/ChangeLog:

	PR tree-optimization/83698
	* gcc.dg/Wrestrict-7.c: New test.
	* c-c++-common/Wrestrict.c: Adjust expected values for strcat.
	* gcc.target/i386/chkp-stropt-17.c: Same.

From-SVN: r257676

gcc/ChangeLog

 2018-02-14  Martin Sebor  <msebor@redhat.com>
 
+	PR tree-optimization/83698
+	* gimple-ssa-warn-restrict.c (builtin_memref::builtin_memref): For
+	arrays constrain the offset range to their bounds.
+	(builtin_access::strcat_overlap): Adjust the bounds of overlap offset.
+	(builtin_access::overlap): Avoid setting the size of overlap if it's
+	already been set.
+	(maybe_diag_overlap): Also consider arrays when deciding what values
+	of offsets to include in diagnostics.
+
+2018-02-14  Martin Sebor  <msebor@redhat.com>
+
 	PR c/84108
 	* attribs.c (diag_attr_exclusions): Consider the exclusion(s)
 	that correspond to the kind of a declaration.

gcc/gimple-ssa-warn-restrict.c

@@ -375,6 +375,14 @@ builtin_memref::builtin_memref (tree expr, tree size)
 	    }
       }
 
+  if (DECL_P (base) && TREE_CODE (TREE_TYPE (base)) == ARRAY_TYPE)
+    {
+      /* For array objects, where a negative offset wouldn't make
+	 sense, use zero instead if the upper bound is positive.  */
+      if (offrange[0] < 0 && offrange[1] > 0)
+	offrange[0] = 0;
+    }
+
   if (size)
     {
       tree range[2];
@@ -1070,14 +1078,35 @@ builtin_access::strcat_overlap ()
     return false;
 
   /* When strcat overlap is certain it is always a single byte:
-     the terminatinn NUL, regardless of offsets and sizes.  When
+     the terminating NUL, regardless of offsets and sizes.  When
      overlap is only possible its range is [0, 1].  */
   acs.ovlsiz[0] = dstref->sizrange[0] == dstref->sizrange[1] ? 1 : 0;
   acs.ovlsiz[1] = 1;
-  acs.ovloff[0] = (dstref->sizrange[0] + dstref->offrange[0]).to_shwi ();
-  acs.ovloff[1] = (dstref->sizrange[1] + dstref->offrange[1]).to_shwi ();
 
-  acs.sizrange[0] = wi::smax (acs.dstsiz[0], srcref->sizrange[0]).to_shwi ();
+  offset_int endoff = dstref->offrange[0] + dstref->sizrange[0];
+  if (endoff <= srcref->offrange[0])
+    acs.ovloff[0] = wi::smin (maxobjsize, srcref->offrange[0]).to_shwi ();
+  else
+    acs.ovloff[0] = wi::smin (maxobjsize, endoff).to_shwi ();
+
+  acs.sizrange[0] = wi::smax (wi::abs (endoff - srcref->offrange[0]) + 1,
+			      srcref->sizrange[0]).to_shwi ();
+  if (dstref->offrange[0] == dstref->offrange[1])
+    {
+      if (srcref->offrange[0] == srcref->offrange[1])
+	acs.ovloff[1] = acs.ovloff[0];
+      else
+	acs.ovloff[1]
+	  = wi::smin (maxobjsize,
+		      srcref->offrange[1] + srcref->sizrange[1]).to_shwi ();
+    }
+  else
+    acs.ovloff[1]
+      = wi::smin (maxobjsize,
+		  dstref->offrange[1] + dstref->sizrange[1]).to_shwi ();
+
+  if (acs.sizrange[0] == 0)
+    acs.sizrange[0] = 1;
   acs.sizrange[1] = wi::smax (acs.dstsiz[1], srcref->sizrange[1]).to_shwi ();
   return true;
 }
@@ -1215,8 +1244,12 @@ builtin_access::overlap ()
   /* Call the appropriate function to determine the overlap.  */
   if ((this->*detect_overlap) ())
     {
+      if (!sizrange[1])
+	{
+	  /* Unless the access size range has already been set, do so here.  */
 	  sizrange[0] = wi::smax (acs.dstsiz[0], srcref->sizrange[0]).to_shwi ();
 	  sizrange[1] = wi::smax (acs.dstsiz[1], srcref->sizrange[1]).to_shwi ();
+	}
       return true;
     }
 
@@ -1392,7 +1425,14 @@ maybe_diag_overlap (location_t loc, gcall *call, builtin_access &acs)
   /* Use more concise wording when one of the offsets is unbounded
      to avoid confusing the user with large and mostly meaningless
      numbers.  */
-  bool open_range = ((dstref.offrange[0] == -maxobjsize - 1
+  bool open_range;
+  if (DECL_P (dstref.base) && TREE_CODE (TREE_TYPE (dstref.base)) == ARRAY_TYPE)
+    open_range = ((dstref.offrange[0] == 0
+		   && dstref.offrange[1] == maxobjsize)
+		  || (srcref.offrange[0] == 0
+		      && srcref.offrange[1] == maxobjsize));
+  else
+    open_range = ((dstref.offrange[0] == -maxobjsize - 1
 		   && dstref.offrange[1] == maxobjsize)
 		  || (srcref.offrange[0] == -maxobjsize - 1
 		      && srcref.offrange[1] == maxobjsize));

gcc/testsuite/ChangeLog

@@ -5,6 +5,13 @@
 
 2018-02-14  Martin Sebor  <msebor@redhat.com>
 
+	PR tree-optimization/83698
+	* gcc.dg/Wrestrict-7.c: New test.
+	* c-c++-common/Wrestrict.c: Adjust expected values for strcat.
+	* gcc.target/i386/chkp-stropt-17.c: Same.
+
+2018-02-14  Martin Sebor  <msebor@redhat.com>
+
 	PR c/84108
 	* gcc.dg/Wattributes-8.c: New test.
 

gcc/testsuite/c-c++-common/Wrestrict.c

@@ -616,10 +616,13 @@ void test_strcat_var (char *d, const char *s)
   } while (0)
 
   T (d, d);                       /* { dg-warning "source argument is the same as destination" "strcat" } */
-  T (d, d + 1);                   /* { dg-warning "accessing 0 or more bytes at offsets 0 and 1 may overlap 1 byte" "strcat" } */
-  T (d, d + 2);                   /* { dg-warning "accessing 0 or more bytes at offsets 0 and 2 may overlap 1 byte" "strcat" } */
-  T (d, d + 999);                 /* { dg-warning "accessing 0 or more bytes at offsets 0 and 999 may overlap 1 byte" "strcat" } */
-  T (d, d + -99);                 /* { dg-warning "accessing 0 or more bytes at offsets 0 and -99 may overlap 1 byte" "strcat" } */
+  T (d, d + 1);                   /* { dg-warning "accessing 2 or more bytes at offsets 0 and 1 may overlap 1 byte" "strcat" } */
+  T (d, d + 2);                   /* { dg-warning "accessing 3 or more bytes at offsets 0 and 2 may overlap 1 byte at offset 2" "strcat" } */
+  T (d, d + 999);                 /* { dg-warning "accessing 1000 or more bytes at offsets 0 and 999 may overlap 1 byte at offset 999" "strcat" } */
+
+  /* The source string must be at least 100 bytes in length for the copy
+     below to overlap.  */
+  T (d, d + -99);                 /* { dg-warning "accessing 100 or more bytes at offsets 0 and -99 may overlap 1 byte" "strcat" } */
 
   size_t n = unsigned_value ();
 

gcc/testsuite/gcc.dg/Wrestrict-7.c

+/* PR tree-optimization/83698 - bogus offset in -Wrestrict messages for
+   strcat of unknown strings
+   { dg-do compile }
+   { dg-options "-O2 -Wrestrict -ftrack-macro-expansion=0" } */
+
+extern char* strcat (char*, const char*);
+
+void sink (char*);
+
+#define T(d, s) sink (strcat (d, s))
+
+extern char arr[];
+
+
+void test_strcat_array_cst_offset (void)
+{
+  T (arr, arr + 1);           /* { dg-warning "accessing 2 or more bytes at offsets 0 and 1 may overlap 1 byte at offset 1" } */
+  T (arr, arr + 2);           /* { dg-warning "accessing 3 or more bytes at offsets 0 and 2 may overlap 1 byte at offset 2" } */
+  T (arr, arr + 13);          /* { dg-warning "accessing 14 or more bytes at offsets 0 and 13 may overlap 1 byte at offset 13" } */
+
+  T (arr + 1, arr);           /* { dg-warning "accessing 2 or more bytes at offsets 1 and 0 may overlap 1 byte at offset 1" } */
+  T (arr + 17, arr + 11);     /* { dg-warning "accessing 7 or more bytes at offsets 17 and 11 may overlap 1 byte at offset 17" } */
+  T (arr + 36, arr + 20);     /* { dg-warning "accessing 17 or more bytes at offsets 36 and 20 may overlap 1 byte at offset 36" } */
+}
+
+void test_strcat_ptr_cst_offset (char *d)
+{
+  T (d - 12, d + 34);         /* { dg-warning "accessing 47 or more bytes at offsets -12 and 34 may overlap 1 byte at offset 34" } */
+  T (d + 12, d + 34);         /* { dg-warning "accessing 23 or more bytes at offsets 12 and 34 may overlap 1 byte at offset 34" } */
+  T (d + 20, d + 36);         /* { dg-warning "accessing 17 or more bytes at offsets 20 and 36 may overlap 1 byte at offset 36" } */
+}
+
+void test_strcat_array_var_offset (int i, int j)
+{
+  T (arr + i, arr);           /* { dg-warning "accessing 1 or more bytes at offsets \\\[0, \[0-9\]+] and 0 may overlap 1 byte at offset \\\[0, \[0-9\]+]" } */
+  T (arr, arr + j);           /* { dg-warning "accessing 1 or more bytes at offsets 0 and \\\[0, \[0-9\]+] may overlap 1 byte at offset \\\[0, \[0-9\]+]" } */
+  T (arr + i, arr + j);       /* { dg-warning "accessing 1 or more bytes at offsets \\\[0, \[0-9\]+] and \\\[0, \[0-9\]+] may overlap 1 byte at offset \\\[0, \[0-9\]+]" } */
+
+  T (arr + i, arr + 5);       /* { dg-warning "accessing 6 or more bytes at offsets \\\[0, \[0-9\]+] and 5 may overlap 1 byte at offset \\\[5, \[0-9\]+]" } */
+  T (arr + 7, arr + j);       /* { dg-warning "accessing 8 or more bytes at offsets 7 and \\\[0, \[0-9\]+] may overlap 1 byte at offset \\\[7, \[0-9\]+]" } */
+}
+
+void test_strcat_ptr_var_offset (char *d, int i, int j)
+{
+  T (d + i, d);               /* { dg-warning "accessing \[0-9\]+ or more bytes at offsets \\\[-\[0-9\]+, \[0-9\]+] and 0 may overlap 1 byte at offset \\\[0, \[0-9\]+]" } */
+  T (d, d + j);               /* { dg-warning "accessing \[0-9\]+ or more bytes at offsets 0 and \\\[-\[0-9\]+, \[0-9\]+] may overlap 1 byte at offset \\\[0, \[0-9\]+]" } */
+  T (d + i, d + j);           /* { dg-warning "accessing 1 or more bytes at offsets \\\[-\[0-9\]+, \[0-9\]+] and \\\[-\[0-9\]+, \[0-9\]+] may overlap 1 byte at offset \\\[-\[0-9\]+, \[0-9\]+]" } */
+
+  T (d + i, d + 3);           /* { dg-warning "accessing \[0-9\]+ or more bytes at offsets \\\[-\[0-9\]+, \[0-9\]+] and 3 may overlap 1 byte at offset \\\[3, \[0-9\]+]" } */
+  T (d + 9, d + j);           /* { dg-warning "accessing \[0-9\]+ or more bytes at offsets 9 and \\\[-\[0-9\]+, \[0-9\]+] may overlap 1 byte at offset \\\[9, \[0-9\]+]" } */
+}

gcc/testsuite/gcc.target/i386/chkp-stropt-17.c

@@ -51,7 +51,7 @@ void test_strcpy (void)
 
 void test_strcat (int n)
 {
-  strcat (a, a + 3);   /* { dg-warning ".strcat\.chkp. accessing 0 or more bytes at offsets 0 and 3 may overlap 1 byte" } */
+  strcat (a, a + 3);   /* { dg-warning ".strcat\.chkp. accessing 4 or more bytes at offsets 0 and 3 may overlap 1 byte at offset 3" } */
 }
 
 void test_strncat (int n)