PR tree-optimization/79352 - -fprintf-return-value doesn't handle flexible-like array members properly

gcc/ChangeLog:

	PR tree-optimization/79352
	* gimple-fold.c (get_range_strlen): Add argument.
	(get_range_strlen): Change return type to bool.
	(get_maxval_strlen): Pass in a dummy argument.
	* gimple-fold.h (get_range_strlen): Change return type to bool.
	* gimple-ssa-sprintf.c (get_string_length): Set unlikely counter.
	* tree.h (array_at_struct_end_p): Add argument.
	* tree.c (array_at_struct_end_p): Handle it.

gcc/testsuite/ChangeLog:

	PR tree-optimization/79352
	* gcc.dg/tree-ssa/pr79352.c: New test.

From-SVN: r245156

1 files changed, 6 insertions, 2 deletions

diff --git a/gcc/gimple-ssa-sprintf.c b/gcc/gimple-ssa-sprintf.c
index 10c6d8e..3670bac 100644
--- a/gcc/gimple-ssa-sprintf.c
+++ b/gcc/gimple-ssa-sprintf.c
@@ -1800,7 +1800,7 @@ get_string_length (tree str)
      aren't known to point any such arrays result in LENRANGE[1] set
      to SIZE_MAX.  */
   tree lenrange[2];
-  get_range_strlen (str, lenrange);
+  bool flexarray = get_range_strlen (str, lenrange);
 
   if (lenrange [0] || lenrange [1])
     {
@@ -1843,7 +1843,11 @@ get_string_length (tree str)
 	  res.range.min = 0;
 	}
 
-      res.range.unlikely = res.range.max;
+      /* If the range of string length has been estimated from the size
+	 of an array at the end of a struct assume that it's longer than
+	 the array bound says it is in case it's used as a poor man's
+	 flexible array member, such as in struct S { char a[4]; };  */
+      res.range.unlikely = flexarray ? HOST_WIDE_INT_MAX : res.range.max;
 
       return res;
     }