[libcamera-devel] [PATCH v1.1 1/5] meson: Switch to C++17

[Laurent Pinchart]

Due to popular request, move from C++14 to C++17. This will allow
dropping some custom constructs (such as a custom utils::clamp),
benefiting from new language features, and dropping gcc 5 and 6 from the
compilation tests.

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
Changes since v1:

- Update documentation
- Print an error message when detecting a too old compiler
---
 Documentation/coding-style.rst |  5 ++---
 meson.build                    | 29 ++++++++++++++++++-----------
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/Documentation/coding-style.rst b/Documentation/coding-style.rst
index 7acba37b8de8..7c56a1b70014 100644
--- a/Documentation/coding-style.rst
+++ b/Documentation/coding-style.rst
@@ -88,13 +88,12 @@ headers, and with double quotes for other libcamera headers.
 C++ Specific Rules
 ------------------
 
-The code shall be implemented in C++14, with the following caveats:
+The code shall be implemented in C++17, with the following caveats:
 
 * Type inference (auto and decltype) shall be used with caution, to avoid
   drifting towards an untyped language.
 * The explicit, override and final specifiers are to be used where applicable.
-* General-purpose smart pointers (std::unique_ptr) deprecate std::auto_ptr.
-  Smart pointers, as well as shared pointers and weak pointers, shall not be
+* Smart pointers, as well as shared pointers and weak pointers, shall not be
   overused.
 * Classes are encouraged to define move constructors and assignment operators
   where applicable, and generally make use of the features offered by rvalue
diff --git a/meson.build b/meson.build
index ec54e68f3635..cf2636d97100 100644
--- a/meson.build
+++ b/meson.build
@@ -6,7 +6,7 @@ project('libcamera', 'c', 'cpp',
     default_options : [
         'werror=true',
         'warning_level=2',
-        'cpp_std=c++14',
+        'cpp_std=c++17',
     ],
     license : 'LGPL 2.1+')
 
@@ -62,6 +62,23 @@ if cc.get_id() == 'clang'
     endif
 endif
 
+if cc.get_id() == 'gcc'
+    if cc.version().version_compare('<7')
+        error('gcc version is too old, libcamera requires 7.0 or newer')
+    endif
+
+    # gcc 7.1 introduced processor-specific ABI breakages related to parameter
+    # passing on ARM platforms. This generates a large number of messages
+    # during compilation with gcc >=7.1 until gcc 9. Silence them.
+    if (host_machine.cpu_family() == 'arm' and
+        cc.version().version_compare('>=7.1') and
+        cc.version().version_compare('<9'))
+        cpp_arguments += [
+            '-Wno-psabi',
+        ]
+    endif
+endif
+
 # We use C99 designated initializers for arrays as C++ has no equivalent
 # feature. Both gcc and clang support this extension, but recent
 # versions of clang generate a warning that needs to be disabled.
@@ -71,16 +88,6 @@ if cc.has_argument('-Wno-c99-designator')
     ]
 endif
 
-# gcc 7.1 introduced processor-specific ABI breakages related to parameter
-# passing on ARM platforms. This generates a large number of messages during
-# compilation with gcc >=7.1 until gcc 9. Silence them.
-if (host_machine.cpu_family() == 'arm' and cc.get_id() == 'gcc' and
-    cc.version().version_compare('>=7.1') and cc.version().version_compare('<9'))
-    cpp_arguments += [
-        '-Wno-psabi',
-    ]
-endif
-
 c_arguments += common_arguments
 cpp_arguments += common_arguments
 
-- 
Regards,

Laurent Pinchart