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https://issues.apache.org/jira/browse/STDCXX-998?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Martin Sebor updated STDCXX-998:
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Attachment: unint_fill_nothrow.ipf.s
Attached disassembly of {{uninit_fill}} for {{S::S()}} declared with the empty
exception specification generated by HP aCC 6.16 at +O2.
> add throw() exception specification to all non-throwing functions
> -----------------------------------------------------------------
>
> Key: STDCXX-998
> URL: https://issues.apache.org/jira/browse/STDCXX-998
> Project: C++ Standard Library
> Issue Type: Improvement
> Components: Build and Installation
> Affects Versions: 4.2.1
> Reporter: Martin Sebor
> Priority: Critical
> Fix For: 4.2.2
>
> Attachments: uninit_fill.ipf.s, unint_fill_nothrow.ipf.s
>
> Original Estimate: 6h
> Remaining Estimate: 6h
>
> When a compiler cannot determine whether a function declared without an
> explicit exception specification may throw an exception or not (e.g., because
> the compiler/optimizer doesn't have access to the definition of the function)
> it must assume that the function may throw and may need to generate
> suboptimal code as a result.
> Compilers often assume that even inline functions that can be proven not to
> throw exceptions may throw unless they are declared with the empty exception
> specification and generates suboptimal code as a result. For example, HP aCC
> 6 assumes that {{S::S()}} in the code below may throw
> and fails to optimize the catch block away, generating object code 2.5 times
> the size bigger than necessary. (Note that gcc 3.4 on IPF generates optimal
> code in this case).
> To help compilers generate optimal code we should make use of the empty
> exception specification on all functions that cannot throw exceptions,
> including those declared explicitly or implicitly {{inline}}.
> {code}
> #include <new>
> struct S {
> int i;
> S () /* throw () */: i () { }
> };
> void uninit_fill (S *a, S *b)
> {
> S *p = a;
> try {
> for ( ; p != b; ++p)
> new (p) S ();
> }
> catch (...) {
> while (p-- != a)
> p->~S ();
> throw;
> }
> }
> {code}
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