[Bug libstdc++/86822] New: attribute((malloc)) for new(nothrow)

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86822

            Bug ID: 86822
           Summary: attribute((malloc)) for new(nothrow)
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: glisse at gcc dot gnu.org
  Target Milestone: ---

In decl.c:cxx_init_decl_processing, the C++ front-end predeclares ::operator
new (normal or vector, aligned or not) and marks it with

DECL_IS_MALLOC (opnew) = 1;

This lets the compiler optimize various things: the result cannot alias, the
result is seldom 0 (still under review), etc.

The nothrow versions of operator new are only declared in <new> and do not have
the equivalent __attribute__((__malloc__)). Unless someone can think of a
reason not to, I think we should add it there.