[gcc r15-515] c++: add test for DR 2855

[Marek Polacek via Gcc-cvs]

https://gcc.gnu.org/g:3cefe91b74f65f0db71472e01ca83c69e2cd81cc

commit r15-515-g3cefe91b74f65f0db71472e01ca83c69e2cd81cc
Author: Marek Polacek <pola...@redhat.com>
Date:   Tue May 14 13:48:30 2024 -0400

    c++: add test for DR 2855
    
    Let
    
      int8_t x = 127;
    
    This DR says that while
    
      x++;
    
    invokes UB,
    
      ++x;
    
    does not.  The resolution was to make the first one valid.  The
    following test verifies that we don't report any errors in a constexpr
    context.
    
            DR 2855
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/DRs/dr2855.C: New test.

Diff:
---
 gcc/testsuite/g++.dg/DRs/dr2855.C | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/gcc/testsuite/g++.dg/DRs/dr2855.C 
b/gcc/testsuite/g++.dg/DRs/dr2855.C
new file mode 100644
index 000000000000..b4609ceaa158
--- /dev/null
+++ b/gcc/testsuite/g++.dg/DRs/dr2855.C
@@ -0,0 +1,16 @@
+// DR 2855, Undefined behavior in postfix increment
+// { dg-do compile { target c++14 } }
+
+using int8_t = signed char;
+
+constexpr int
+f ()
+{
+  int8_t x = 127;
+  x++;
+  int8_t z = 127;
+  ++z;
+  return x + z;
+}
+
+constexpr int i = f();