Daniel Carvalho has submitted this change. (
https://gem5-review.googlesource.com/c/public/gem5/+/45246 )
Change subject: base: Add macros to deprecate namespaces and classes
......................................................................
base: Add macros to deprecate namespaces and classes
The GEM5_DEPRECATED_NAMESPACE macro temporarily declares
a namespace with the deprecated name that prints a
warning message when used. It also make sure that when
the old namespace name is used the new name is referenced.
The GEM5_DEPRECATED_CLASS macro deprecates classes that
were renamed, or moved to different namespaces.
Attributes in namespaces are an issue, though.
- Clang only allows from version 6 on, and only when
using C++17.
- GCC has a bug before version 10 where the deprecated
attribute was not properly recognized in namespaces:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79817
Possible solutions for GCC < 10:
1)
\#define GEM5_DEPRECATED_NAMESPACE() \
namespace gem5 { namespace deprecated { \
auto namespace_##old_namespace = [](){ \
GEM5_DEPRECATED("Please use the new namespace: '" \
\#new_namespace "'") \
int old_namespace; \
return old_namespace; \
}; \
}} \
namespace new_namespace {} \
namespace old_namespace { \
using namespace new_namespace; \
}
Add the above macro to all headers that previously
declared the deprecated namespace to trigger a
warning. This is extremely inconvenient because
every file that includes that header will trigger
the deprecation warning, so the compilation output
gets VERY clogged.
2) Similar to 1), but do not use the temporary variable
on declaration. This would require using the variable
somewhere else, like a respective .c file. This is
not always possible, so we could resort to adding a
special file (e.g., base/deprecated_elements.cc)
containing all uses of the deprecated temporary
variables.
3)
\#define GEM5_DEPRECATED_NAMESPACE(old_ns, new_ns) \
namespace old_ns = new_ns;
Similar to 3), but simply declare an alias in the
header files (see above macro) to maintain backwards
compatibility. Then use the special file to declare
all deprecation messages.
4)
Rely on release notes / e-mail to the mailing list
to inform that those are deprecated.
We have selected option 4 for these problematic instances.
Checking if namespace deprecation is possible is done
through scons.
Jira issues:
https://gem5.atlassian.net/browse/GEM5-975
https://gem5.atlassian.net/browse/GEM5-991
Change-Id: Ide234f6a8707d88a869fa843bf8c61ca7714e4f3
Signed-off-by: Daniel R. Carvalho <[email protected]>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/45246
Reviewed-by: Jason Lowe-Power <[email protected]>
Maintainer: Jason Lowe-Power <[email protected]>
Tested-by: kokoro <[email protected]>
---
M src/base/SConsopts
M src/base/compiler.hh
2 files changed, 39 insertions(+), 1 deletion(-)
Approvals:
Jason Lowe-Power: Looks good to me, approved; Looks good to me, approved
kokoro: Regressions pass
diff --git a/src/base/SConsopts b/src/base/SConsopts
index 9b301c3..ea11bd4 100644
--- a/src/base/SConsopts
+++ b/src/base/SConsopts
@@ -56,10 +56,20 @@
# alternative stacks.
conf.env['HAVE_VALGRIND'] = conf.CheckCHeader('valgrind/valgrind.h')
+ conf.env['HAVE_DEPRECATED_NAMESPACE'] = conf.TryCompile('''
+ int main() {return 0;}
+ namespace [[gnu::deprecated("Test namespace deprecation")]]
+ test_deprecated_namespace {}
+ ''', '.cc')
+ if not conf.env['HAVE_DEPRECATED_NAMESPACE']:
+ warning("Deprecated namespaces are not supported by this
compiler.\n"
+ "Please make sure to check the mailing list for
deprecation "
+ "announcements.")
sticky_vars.Add(BoolVariable('USE_POSIX_CLOCK', 'Use POSIX Clocks',
have_posix_clock))
export_vars.extend([
- 'HAVE_FENV', 'HAVE_PNG', 'USE_POSIX_CLOCK', 'HAVE_VALGRIND'])
+ 'HAVE_FENV', 'HAVE_PNG', 'USE_POSIX_CLOCK', 'HAVE_VALGRIND',
+ 'HAVE_DEPRECATED_NAMESPACE'])
diff --git a/src/base/compiler.hh b/src/base/compiler.hh
index 17124be..8fd3808 100644
--- a/src/base/compiler.hh
+++ b/src/base/compiler.hh
@@ -43,6 +43,8 @@
#include <memory>
+#include "config/have_deprecated_namespace.hh"
+
// http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
@@ -138,6 +140,32 @@
# define GEM5_DEPRECATED_MACRO_STMT(name, definition, message) \
do {{definition;} GEM5_DEPRECATED_MACRO(name, {}, message);} while (0)
+// To mark a class as deprecated in favor of a new name, add a respective
+// instance of this macro to the file that used to declare the old name.
+// This macro should be used *after* the new class has been defined.
+# define GEM5_DEPRECATED_CLASS(old_class, new_class) \
+ using old_class \
+ GEM5_DEPRECATED("Please use the new class name: '" #new_class "'")
= \
+ new_class
+
+// These macros should be used when namespaces are deprecated in favor of
+// a new name. They should be used wherever the namespace is declared.
+// Namespace deprecation is broken for GNU < 10 [1], so there is no
+// deprecation warning in that case. Clang only supports it from C++17 on.
+// [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79817
+# if HAVE_DEPRECATED_NAMESPACE
+# define GEM5_DEPRECATED_NAMESPACE(old_namespace, new_namespace) \
+ namespace new_namespace {} \
+ namespace GEM5_DEPRECATED("Please use the new namespace: '" \
+ #new_namespace "'") old_namespace { \
+ using namespace new_namespace; \
+ }
+# else
+# define GEM5_DEPRECATED_NAMESPACE(old_namespace, new_namespace) \
+ namespace new_namespace {} \
+ namespace old_namespace = new_namespace
+# endif
+
// Evaluate an expanded parameter pack in order. Multiple arguments can be
// passed in which be evaluated in order relative to each other as a group.
// The argument(s) must include a parameter pack to expand. This works
because
--
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Gerrit-Project: public/gem5
Gerrit-Branch: develop
Gerrit-Change-Id: Ide234f6a8707d88a869fa843bf8c61ca7714e4f3
Gerrit-Change-Number: 45246
Gerrit-PatchSet: 7
Gerrit-Owner: Daniel Carvalho <[email protected]>
Gerrit-Reviewer: Bobby R. Bruce <[email protected]>
Gerrit-Reviewer: Daniel Carvalho <[email protected]>
Gerrit-Reviewer: Gabe Black <[email protected]>
Gerrit-Reviewer: Giacomo Travaglini <[email protected]>
Gerrit-Reviewer: Jason Lowe-Power <[email protected]>
Gerrit-Reviewer: Jason Lowe-Power <[email protected]>
Gerrit-Reviewer: kokoro <[email protected]>
Gerrit-MessageType: merged
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