diff mbox series

c++: add test for DR 2855

Message ID 20240514175414.879379-1-polacek@redhat.com
State New
Headers show
Series c++: add test for DR 2855 | expand

Commit Message

Marek Polacek May 14, 2024, 5:54 p.m. UTC 
Tested x86_64-pc-linux-gnu, OK to add such a test?

-- >8 --
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.
---
 gcc/testsuite/g++.dg/DRs/dr2855.C | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/DRs/dr2855.C


base-commit: c290e6a0b7a9de5692963affc6627a4af7dc2411

Comments

Jason Merrill May 14, 2024, 9:22 p.m. UTC | #1 
On 5/14/24 13:54, Marek Polacek wrote:
> Tested x86_64-pc-linux-gnu, OK to add such a test?

OK.

> -- >8 --
> 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.
> ---
>   gcc/testsuite/g++.dg/DRs/dr2855.C | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/DRs/dr2855.C
> 
> diff --git a/gcc/testsuite/g++.dg/DRs/dr2855.C b/gcc/testsuite/g++.dg/DRs/dr2855.C
> new file mode 100644
> index 00000000000..b4609ceaa15
> --- /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();
> 
> base-commit: c290e6a0b7a9de5692963affc6627a4af7dc2411
diff mbox series

Patch

diff --git a/gcc/testsuite/g++.dg/DRs/dr2855.C b/gcc/testsuite/g++.dg/DRs/dr2855.C
new file mode 100644
index 00000000000..b4609ceaa15
--- /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();