Hi Branden,
When compiling Groff with GCC/G++ 15.0, I run into this compiler error:
CXX src/roff/troff/div.o
In file included from src/roff/troff/div.cpp:29:
src/roff/troff/hvunits.h: In member function ‘units vunits::to_units()’:
src/roff/troff/hvunits.h:91:7: error: ‘ckd_mul’ was not declared in this
scope
91 | if (ckd_mul(&r, n, vresolution))
| ^~~~~~~
src/roff/troff/hvunits.h: In function ‘vunits operator+(const vunits&,
const vunits&)’:
src/roff/troff/hvunits.h:105:7: error: ‘ckd_add’ was not declared in this
scope
105 | if (ckd_add(&r.n, r.n, y.n))
This is because in /usr/include/c++/15/stdckdint.h
#if __cplusplus > 202302L
/* Template wizardry to define ckd_*. */
#endif
The immediate fix that comes to mind is using 'g++ -std=gnu23', but
there are 2 issues with this:
1. gnulib/m4/std-gnu23.m4 has no code for C++ versions, because no
one interested in C++ has contributed it to Autoconf yet.
2. Bruno told me that the C++ standards are not compatible with each
other, so there would probably be more issues caused by the change
[1].
I have committed the two attached patches to Gnulib. If the system has
<stdbit.h> and C++ is in use, we just generate <stdbit.h> and include
it. That way these macros will be defined.
My assumption here is that if a system is modern enough to have
<stdbit.h> it's C++ compiler supports __builtin_*_overflow. Since I
assume lib/intprops.h is not compatible with C++. This should be true
for GCC and Clang. For MSVC, I will probably have to add C++
templates...
[1] https://lists.gnu.org/archive/html/bug-gnulib/2025-04/msg00176.html
>From 5948807b3e200214799d323d9784e74fa5f72e23 Mon Sep 17 00:00:00 2001
Message-ID: <5948807b3e200214799d323d9784e74fa5f72e23.1747715373.git.collin.fu...@gmail.com>
From: Collin Funk <[email protected]>
Date: Mon, 19 May 2025 21:23:56 -0700
Subject: [PATCH 1/2] stdckdint-h C++ tests: Verify the ckd_* functions can be
invoked.
* tests/test-stdckdint-h-c++.cc (main): Invoke ckd_add, ckd_sub, and
ckd_mul.
---
ChangeLog | 6 ++++++
tests/test-stdckdint-h-c++.cc | 6 ++++++
2 files changed, 12 insertions(+)
diff --git a/ChangeLog b/ChangeLog
index 75792d4fe2..2351f847ef 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2025-05-19 Collin Funk <[email protected]>
+
+ stdckdint-h C++ tests: Verify the ckd_* functions can be invoked.
+ * tests/test-stdckdint-h-c++.cc (main): Invoke ckd_add, ckd_sub, and
+ ckd_mul.
+
2025-05-18 Paul Eggert <[email protected]>
tests: simplify test_exit_status decl
diff --git a/tests/test-stdckdint-h-c++.cc b/tests/test-stdckdint-h-c++.cc
index 00680385cf..071d7be740 100644
--- a/tests/test-stdckdint-h-c++.cc
+++ b/tests/test-stdckdint-h-c++.cc
@@ -25,4 +25,10 @@
int
main ()
{
+ /* We only check that the macros can be invoked here. The actual tests are
+ performed by the C program. */
+ int r;
+ int a = 1;
+ int b = 1;
+ return !!(ckd_add (&r, a, b) || ckd_sub (&r, a, b) || ckd_mul (&r, a, b));
}
--
2.49.0
>From 7ee6e40b6730c87e5c1323bb5c2564bcb6eff9e4 Mon Sep 17 00:00:00 2001
Message-ID: <7ee6e40b6730c87e5c1323bb5c2564bcb6eff9e4.1747715373.git.collin.fu...@gmail.com>
In-Reply-To: <5948807b3e200214799d323d9784e74fa5f72e23.1747715373.git.collin.fu...@gmail.com>
References: <5948807b3e200214799d323d9784e74fa5f72e23.1747715373.git.collin.fu...@gmail.com>
From: Collin Funk <[email protected]>
Date: Mon, 19 May 2025 21:29:03 -0700
Subject: [PATCH 2/2] stdckdint-h: Work around missing declarations with g++
15.0.
* modules/stdckdint-h (configure.ac): Generate the header if the system
has one and C++ is being used.
---
ChangeLog | 4 ++++
modules/stdckdint-h | 6 +++++-
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/ChangeLog b/ChangeLog
index 2351f847ef..b85c7c6e6e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
2025-05-19 Collin Funk <[email protected]>
+ stdckdint-h: Work around missing declarations with g++ 15.0.
+ * modules/stdckdint-h (configure.ac): Generate the header if the system
+ has one and C++ is being used.
+
stdckdint-h C++ tests: Verify the ckd_* functions can be invoked.
* tests/test-stdckdint-h-c++.cc (main): Invoke ckd_add, ckd_sub, and
ckd_mul.
diff --git a/modules/stdckdint-h b/modules/stdckdint-h
index 24e26cfb69..ff777d8d62 100644
--- a/modules/stdckdint-h
+++ b/modules/stdckdint-h
@@ -12,7 +12,11 @@ bool
configure.ac:
AC_CHECK_HEADERS_ONCE([stdckdint.h])
if test $ac_cv_header_stdckdint_h = yes; then
- GL_GENERATE_STDCKDINT_H=false
+ if test -n "$CXX" && test "$CXX" != no; then
+ GL_GENERATE_STDCKDINT_H=true
+ else
+ GL_GENERATE_STDCKDINT_H=false
+ fi
else
GL_GENERATE_STDCKDINT_H=true
fi
--
2.49.0
