Hi, I don't see the usage on NORETURN attribute and UNREACHABLE() macro. Why we need to add them also?
Thanks Liming > -----Original Message----- > From: Marvin Häuser [mailto:[email protected]] > Sent: Saturday, June 11, 2016 5:02 AM > To: [email protected] > Cc: Gao, Liming <[email protected]>; Kinney, Michael D > <[email protected]> > Subject: [PATCH v1 1/2] MdePkg: Add NORETURN attribute and > UNREACHABLE() macro. > > The NORETURN attribute informs compilers and analyzers that the flagged > function cannot return. This may improve the quality of the optimizations. > > The UNREACHABLE() macro informs compilers and analyzers that its position > cannot be reached, for example eliminating implicit returns. > It is recommended to be used together with the NORETURN attribute to > prevent > warnings regarding the function flagged as 'noreturn' returning. > > The ANALYZER-prefixed versions have the same effects, but exclude > compilers. > They may be used to surpress warnings of static analyzers, such as possible > dereferencing of a NULL pointer when dereferencing it after having checked > it > via ASSERT(). > > Contributed-under: TianoCore Contribution Agreement 1.0 > Signed-off-by: Marvin Haeuser <[email protected]> > --- > MdePkg/Include/Base.h | 103 ++++++++++++++++++++ > 1 file changed, 103 insertions(+) > > diff --git a/MdePkg/Include/Base.h b/MdePkg/Include/Base.h > index 89b2aed07229..9dfafb282177 100644 > --- a/MdePkg/Include/Base.h > +++ b/MdePkg/Include/Base.h > @@ -85,6 +85,109 @@ VERIFY_SIZE_OF (CHAR16, 2); > #endif > > // > +// Should be used in combination with NORETURN to avoid 'noreturn' > returns > +// warnings. > +// > +#ifndef UNREACHABLE > + #ifdef __GNUC__ > + /// > + /// Signal compilers and analyzers that this call is not reachable. It > is > + /// up to the compiler to remove any code past that point. > + /// > + #define UNREACHABLE() __builtin_unreachable() > + #elif defined (__has_feature) > + #if __has_builtin (__builtin_unreachable) > + /// > + /// Signal compilers and analyzers that this call is not reachable. > It is > + /// up to the compiler to remove any code past that point. > + /// > + #define UNREACHABLE() __builtin_unreachable() > + #endif > + #endif > + > + #ifndef UNREACHABLE > + /// > + /// Signal compilers and analyzers that this call is not reachable. It > is > + /// up to the compiler to remove any code past that point. > + /// > + #define UNREACHABLE() > + #endif > +#endif > + > +// > +// Signaling compilers and analyzers that a certain function cannot return > may > +// remove all following code and thus lead to better optimization and less > +// false positives. > +// > +#ifndef NORETURN > + #ifdef __GNUC__ > + /// > + /// Signal compilers and analyzers that the function cannot return. > + /// It is up to the compiler to remove any code past a call to functions > + /// flagged with this attribute. > + /// > + #define NORETURN __attribute__ ((noreturn)) > + #else > + /// > + /// Signal compilers and analyzers that the function cannot return. > + /// It is up to the compiler to remove any code past a call to functions > + /// flagged with this attribute. > + /// > + #define NORETURN > + #endif > +#endif > + > +// > +// Should be used in combination with ANALYZER_NORETURN to avoid > 'noreturn' > +// returns warnings. > +// > +#ifndef ANALYZER_UNREACHABLE > + #ifdef __clang_analyzer__ > + #if __has_builtin (__builtin_unreachable) > + /// > + /// Signal the analyzer that this call is not reachable. > + /// This excludes compilers. > + /// > + #define ANALYZER_UNREACHABLE() __builtin_unreachable() > + #endif > + #endif > + > + #ifndef ANALYZER_UNREACHABLE > + /// > + /// Signal the analyzer that this call is not reachable. > + /// This excludes compilers. > + /// > + #define ANALYZER_UNREACHABLE() > + #endif > +#endif > + > +// > +// Static Analyzers may issue errors about potential NULL-dereferences > when > +// dereferencing a pointer, that has been checked before, outside of a > +// NULL-check. This may lead to false positives, such as when using ASSERT() > +// for verification. > +// > +#ifndef ANALYZER_NORETURN > + #ifdef __has_feature > + #if __has_feature (attribute_analyzer_noreturn) > + /// > + /// Signal analyzers that the function cannot return. > + /// This excludes compilers. > + /// > + #define ANALYZER_NORETURN __attribute__ ((analyzer_noreturn)) > + #endif > + #endif > + > + #ifndef ANALYZER_NORETURN > + /// > + /// Signal the analyzer that the function cannot return. > + /// This excludes compilers. > + /// > + #define ANALYZER_NORETURN > + #endif > +#endif > + > +// > // For symbol name in assembly code, an extra "_" is sometimes necessary > // > > -- > 2.7.4.windows.1 _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
