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| author | Wyatt Hepler <hepler@google.com> | 2022-02-23 11:02:28 -0800 |
|---|---|---|
| committer | CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com> | 2022-03-23 18:14:14 +0000 |
| commit | a996a5ecc8dbcf3b40fc7b9e7fb36b9ea3c9db16 (patch) | |
| tree | c592204dc8c89c40656d5824f43a6d211d8b28d0 /pw_preprocessor/public | |
| parent | 9f29451249c25f28f504bc6148e5a5612c4dcd94 (diff) | |
| download | pigweed-a996a5ecc8dbcf3b40fc7b9e7fb36b9ea3c9db16.tar.gz | |
pw_preprocessor: PW_HAVE_CPP_ATTRIBUTE and new attribute
- PW_HAVE_CPP_ATTRIBUTE() checks if a C++-style attribute is supported.
- PW_ATTRIBUTE_LIFETIME_BOUND marks a returned reference as having a
lifetime bound to a containing object.
Change-Id: I59f2c8f7d7c8c1c1866a70ebd234b867f2377fd7
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/85521
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Reviewed-by: Ewout van Bekkum <ewout@google.com>
Commit-Queue: Wyatt Hepler <hepler@google.com>
Diffstat (limited to 'pw_preprocessor/public')
| -rw-r--r-- | pw_preprocessor/public/pw_preprocessor/compiler.h | 36 |
1 files changed, 35 insertions, 1 deletions
diff --git a/pw_preprocessor/public/pw_preprocessor/compiler.h b/pw_preprocessor/public/pw_preprocessor/compiler.h index d682260b4..690a061b9 100644 --- a/pw_preprocessor/public/pw_preprocessor/compiler.h +++ b/pw_preprocessor/public/pw_preprocessor/compiler.h @@ -127,7 +127,17 @@ #define PW_HAVE_ATTRIBUTE(x) __has_attribute(x) #else #define PW_HAVE_ATTRIBUTE(x) 0 -#endif +#endif // __has_attribute + +// A function-like feature checking macro that accepts C++11 style attributes. +// It's a wrapper around __has_cpp_attribute +// (https://en.cppreference.com/w/cpp/feature_test), borrowed from +// ABSL_HAVE_CPP_ATTRIBUTE. If there is no __has_cpp_attribute, evaluates to 0. +#if defined(__cplusplus) && defined(__has_cpp_attribute) +#define PW_HAVE_CPP_ATTRIBUTE(x) __has_cpp_attribute(x) +#else +#define PW_HAVE_CPP_ATTRIBUTE(x) 0 +#endif // defined(__cplusplus) && defined(__has_cpp_attribute) #define _PW_REQUIRE_SEMICOLON \ static_assert(1, "This macro must be terminated with a semicolon") @@ -182,3 +192,27 @@ // // Driver handler replaced with default unless overridden. // void USART_DriverHandler(void) PW_ALIAS(DefaultDriverHandler); #define PW_ALIAS(aliased_to) __attribute__((weak, alias(#aliased_to))) + +// PW_ATTRIBUTE_LIFETIME_BOUND indicates that a resource owned by a function +// parameter or implicit object parameter is retained by the return value of the +// annotated function (or, for a parameter of a constructor, in the value of the +// constructed object). This attribute causes warnings to be produced if a +// temporary object does not live long enough. +// +// When applied to a reference parameter, the referenced object is assumed to be +// retained by the return value of the function. When applied to a non-reference +// parameter (for example, a pointer or a class type), all temporaries +// referenced by the parameter are assumed to be retained by the return value of +// the function. +// +// See also the upstream documentation: +// https://clang.llvm.org/docs/AttributeReference.html#lifetimebound +// +// This is a copy of ABSL_ATTRIBUTE_LIFETIME_BOUND. +#if PW_HAVE_CPP_ATTRIBUTE(clang::lifetimebound) +#define PW_ATTRIBUTE_LIFETIME_BOUND [[clang::lifetimebound]] +#elif PW_HAVE_ATTRIBUTE(lifetimebound) +#define PW_ATTRIBUTE_LIFETIME_BOUND __attribute__((lifetimebound)) +#else +#define PW_ATTRIBUTE_LIFETIME_BOUND +#endif // PW_ATTRIBUTE_LIFETIME_BOUND |