>From 931d22eb17dca7efc9c355176fe3303d3ab33bb9 Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Fri, 14 Apr 2017 18:55:42 -0700
Subject: [PATCH 2/2] intprops: try to avoid tickling similar bugs

* lib/intprops.h (_GL_INT_OP_CALC): Document that UT no longer
needs to be the same width as T; it can be wider.
Change callers so that UT is at least as wide as unsigned int,
as I suspect that this is less likely to run into compiler bugs.
---
 ChangeLog      |  6 ++++++
 lib/intprops.h | 19 +++++++++----------
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 97d1e59..5ed1517 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2017-04-14  Paul Eggert  <address@hidden>
 
+	intprops: try to avoid tickling similar bugs
+	* lib/intprops.h (_GL_INT_OP_CALC): Document that UT no longer
+	needs to be the same width as T; it can be wider.
+	Change callers so that UT is at least as wide as unsigned int,
+	as I suspect that this is less likely to run into compiler bugs.
+
 	intprops: port to Oracle Studio 12.3 x86
 	Problem reported by Gavin Smith in:
 	http://lists.gnu.org/archive/html/bug-gnulib/2017-04/msg00049.html
diff --git a/lib/intprops.h b/lib/intprops.h
index 220b509..ca8740d 100644
--- a/lib/intprops.h
+++ b/lib/intprops.h
@@ -389,10 +389,10 @@ verify (TYPE_WIDTH (unsigned int) == UINT_WIDTH);
    (_Generic \
     (*(r), \
      signed char: \
-       _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned char, \
+       _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
                         signed char, SCHAR_MIN, SCHAR_MAX), \
      short int: \
-       _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned short int, \
+       _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
                         short int, SHRT_MIN, SHRT_MAX), \
      int: \
        _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
@@ -406,10 +406,10 @@ verify (TYPE_WIDTH (unsigned int) == UINT_WIDTH);
 #else
 # define _GL_INT_OP_WRAPV(a, b, r, op, builtin, overflow) \
    (sizeof *(r) == sizeof (signed char) \
-    ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned char, \
+    ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
                        signed char, SCHAR_MIN, SCHAR_MAX) \
     : sizeof *(r) == sizeof (short int) \
-    ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned short int, \
+    ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
                        short int, SHRT_MIN, SHRT_MAX) \
     : sizeof *(r) == sizeof (int) \
     ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
@@ -431,9 +431,8 @@ verify (TYPE_WIDTH (unsigned int) == UINT_WIDTH);
 
 /* Store the low-order bits of A <op> B into *R, where the operation
    is given by OP.  Use the unsigned type UT for calculation to avoid
-   overflow problems.  *R's type is T, with extremal values TMIN and
-   TMAX.  T must be a signed integer type.  Return 1 if the result
-   overflows.  */
+   overflow problems.  *R's type is T, with extrema TMIN and TMAX.
+   T must be a signed integer type.  Return 1 if the result overflows.  */
 #define _GL_INT_OP_CALC(a, b, r, op, overflow, ut, t, tmin, tmax) \
   (sizeof ((a) op (b)) < sizeof (t) \
    ? _GL_INT_OP_CALC1 ((t) (a), (t) (b), r, op, overflow, ut, t, tmin, tmax) \
@@ -449,9 +448,9 @@ verify (TYPE_WIDTH (unsigned int) == UINT_WIDTH);
    low-order bits of the mathematically-correct answer.  Use the
    unsigned type UT for calculation to avoid undefined behavior on
    signed integer overflow.  Assume that conversion to the result type
-   T yields the low-order bits in the usual way.  UT and T are the
-   same width, T is two's complement, and there is no padding or trap
-   representations.
+   T yields the low-order bits in the usual way.  UT is at least as
+   wide as T and is no narrower than unsigned int, T is two's
+   complement, and there is no padding or trap representations.
 
    According to the C standard, converting UT to T yields an
    implementation-defined result or signal for values outside T's range.
-- 
2.9.3