search for: local_unwind

Hi, Per Reid’s feedback, I have separated two SEH missing features. This thread now is only focusing on _local_unwind(), Jumping out of _finally. The design is documented in Wiki here: https://github.com/tentzen/llvm-project/wiki/Windows-SEH:-Local_Unwind-(aka:-Jumping-Out-of-_Finally) The implementation can be seen here: https://github.com/tentzen/llvm-project/compare/SEH-LU-base...SEH-LU?expand=1 There are onl...

...'m more concerned about. -Eli From: Ten Tzen <tentzen at microsoft.com> Sent: Wednesday, April 1, 2020 7:55 PM To: Eli Friedman <efriedma at quicinc.com>; llvm-dev <llvm-dev at lists.llvm.org> Cc: aaron.smith at microsoft.com Subject: [EXT] RE: [llvm-dev] [RFC] [Windows SEH] Local_Unwind (Jumping out of a _finally) and -EHa (Hardware Exception Handling) ? Take your example, replace "_try" with C++ "try", replace the "_finally" with "catch(....)" with a "throw;" at the end of the catch block, replace the "_except()" wit...

Reply inline From: Ten Tzen <tentzen at microsoft.com> Sent: Wednesday, April 1, 2020 3:54 PM To: Eli Friedman <efriedma at quicinc.com>; llvm-dev <llvm-dev at lists.llvm.org> Cc: aaron.smith at microsoft.com Subject: [EXT] RE: [llvm-dev] [RFC] [Windows SEH] Local_Unwind (Jumping out of a _finally) and -EHa (Hardware Exception Handling) ? For goto in finally, why are you inventing a completely new mechanism for handling this sort of construct? What makes this different from our existing handling of goto out of catch blocks? Maybe there's something obvious...

Resending; I accidentally dropped llvm-dev. -Eli From: Eli Friedman Sent: Wednesday, April 1, 2020 1:01 PM To: Ten Tzen <tentzen at microsoft.com> Cc: aaron.smith at microsoft.com Subject: RE: [EXT] [llvm-dev] [RFC] [Windows SEH] Local_Unwind (Jumping out of a _finally) and -EHa (Hardware Exception Handling) This looks like it outlines the implementation pretty well. For goto in finally, why are you inventing a completely new mechanism for handling this sort of construct? What makes this different from our existing handling of goto o...

...outside of the _finally clause, a "local-unwind" must be triggered to properly invoke _finally clauses alone the path from the goto statement to the target label. Since _finally clause can be executed in either "normal execution path" as well as "exception path", the _local_unwind can take place in both paths too. Let's demonstrate all possible paths in the following example. try { try { try { /* set counter = 1 */ Counter += 1; if (ex) RtlRaiseException(&ExceptionRecord); } finally { Counter += 1; if (abnorm...

...ous Windows SEH RFC below. This RFC only focus on supporting HW Exception Handling. A detailed implementation can be seen in here: https://github.com/tentzen/llvm-project/commit/8a2421c274b683051e456cbe12c177e3b934fb5e It passes all MSVC SEH suite (excluding those with “Jumping out of _finally” ( _Local_Unwind)). Thanks, --Ten **** The rules for C code: **** For C-code, one way (MSVC approach) to achieve SEH -EHa semantic is to follow three rules. First, no exception can move in or out of _try region., i.e., no "potential faulty instruction can be moved across _try boundary. S...

...e&data=02%7C01%7Ctentzen%40microsoft.com%7C334ed759562941d3f2ba08d7e194d0d6%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637225901600853320&sdata=Dx710jfERAD7dDrNvsuEFOYVOrYgeYcRLAlt3mmW8es%3D&reserved=0> It passes all MSVC SEH suite (excluding those with “Jumping out of _finally” ( _Local_Unwind)). Thanks, --Ten **** The rules for C code: **** For C-code, one way (MSVC approach) to achieve SEH -EHa semantic is to follow three rules. First, no exception can move in or out of _try region., i.e., no "potential faulty instruction can be moved across _try boundary. S...

...data=02%7C01%7Ctentzen%40microsoft.com%7C33176bc44b81431207c808d7e1e5e5d8%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637226249850799028&sdata=1oIbyAttvZLWbe5dEa3ROBG16D6sS%2F5A8%2BQRyU6P%2Fa4%3D&reserved=0> It passes all MSVC SEH suite (excluding those with “Jumping out of _finally” ( _Local_Unwind)). Thanks, --Ten **** The rules for C code: **** For C-code, one way (MSVC approach) to achieve SEH -EHa semantic is to follow three rules. First, no exception can move in or out of _try region., i.e., no "potential faulty instruction can be moved across _try boundary. S...