[jira] [Resolved] (IMPALA-3181) build most of impala with -fno-exceptions

["Tim Armstrong (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-3181?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tim Armstrong resolved IMPALA-3181.
-----------------------------------
    Resolution: Later

I think weeding all these references out would be extremely challenging and I don't think we have anyone wanting to drive this, so I'll close for now.

> build most of impala with -fno-exceptions
> -----------------------------------------
>
>                 Key: IMPALA-3181
>                 URL: https://issues.apache.org/jira/browse/IMPALA-3181
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>    Affects Versions: Impala 2.5.0
>            Reporter: Daniel Hecht
>            Assignee: Michael Ho
>            Priority: Minor
>
> In the backend, we only use exceptions when interfacing with third party libraries that throw exceptions (e.g. boost), which we wrap with try-catch. Outside of that, we don't expect, nor handle, exceptions unwinding impala code.
> So, we could isolate calls to those thirdparty libraries to .cc files, and then compile the rest of Impala with -fno-exceptions.  The advantages to doing so are:
> * Better code. All the stack unwinding code goes away and potentially more optimizations are possible.
> * We'll get compiler errors if try-catch is written in places where it won't work anyway (IR code since we disable generating exception handling code). This probably could have caught IMPALA-2184 at compile time.
> A good starting point is probably to turn on -fno-exceptions for IR since we already don't generate exception handling code.  This may require refactoring use of boost headers, however, since statically exceptions may be possible on these paths.
> An alternative would be to use 'noexcept', but this would require annotating every function.
> Example:
> {code}
> #include <stdio.h>
> struct Foo {
>   Foo() { printf("Foo()"); }
>   ~Foo() { printf("~Foo()"); }
> };
> void NoExcept() noexcept;
> void Except();
> void CallNoExcept() {
>   Foo foo;
>   NoExcept();
> }
> void CallExcept() {
>   Foo foo;
>   Except();
> }
> int main() {
>   CallExcept();
> }
> {code}
> {code:title="-std=c++11 -O2 -S"}
> CallNoExcept():
> .LFB18:
>         .cfi_startproc
>         .cfi_personality 0x3,__gxx_personality_v0
>         .cfi_lsda 0x3,.LLSDA18
>         subq    $8, %rsp
>         .cfi_def_cfa_offset 16
>         movl    $.LC0, %edi
>         xorl    %eax, %eax
> .LEHB0:
>         call    printf
> .LEHE0:
>         call    NoExcept()
>         movl    $.LC1, %edi
>         xorl    %eax, %eax
>         addq    $8, %rsp
>         .cfi_def_cfa_offset 8
>         jmp     printf
>         .cfi_endproc
> ...
> CallExcept():
> .LFB19:
>         .cfi_startproc
>         .cfi_personality 0x3,__gxx_personality_v0
>         .cfi_lsda 0x3,.LLSDA19
>         pushq   %rbx
>         .cfi_def_cfa_offset 16
>         .cfi_offset 3, -16
>         movl    $.LC0, %edi
>         xorl    %eax, %eax
> .LEHB1:
>         call    printf
> .LEHE1:
> .LEHB2:
>         call    Except()
> .LEHE2:
>         popq    %rbx
>         .cfi_remember_state
>         .cfi_def_cfa_offset 8
>         movl    $.LC1, %edi
>         xorl    %eax, %eax
>         jmp     printf
> .L5:
>         .cfi_restore_state
>         movq    %rax, %rbx
>         movl    $.LC1, %edi
>         xorl    %eax, %eax
>         call    printf
>         movq    %rbx, %rdi
> .LEHB3:
>         call    _Unwind_Resume
> .LEHE3:
>         .cfi_endproc
> {code}
> {code:title="-std=c++11 -O2 -fno-exceptions -S"}
> CallNoExcept():
> .LFB18:
>         .cfi_startproc
>         subq    $8, %rsp
>         .cfi_def_cfa_offset 16
>         movl    $.LC0, %edi
>         xorl    %eax, %eax
>         call    printf
>         call    NoExcept()
>         movl    $.LC1, %edi
>         xorl    %eax, %eax
>         addq    $8, %rsp
>         .cfi_def_cfa_offset 8
>         jmp     printf
>         .cfi_endproc
> ...
> CallExcept():
> .LFB19:
>         .cfi_startproc
>         subq    $8, %rsp
>         .cfi_def_cfa_offset 16
>         movl    $.LC0, %edi
>         xorl    %eax, %eax
>         call    printf
>         call    Except()
>         movl    $.LC1, %edi
>         xorl    %eax, %eax
>         addq    $8, %rsp
>         .cfi_def_cfa_offset 8
>         jmp     printf
>         .cfi_endproc
> {code}



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