[Bug middle-end/70638] New: transaction_wrap: too strict compatibility check and transaction_pure wrappers fail to wrap

[torvald at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70638

            Bug ID: 70638
           Summary: transaction_wrap: too strict compatibility check and
                    transaction_pure wrappers fail to wrap
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: torvald at gcc dot gnu.org
  Target Milestone: ---

The attached test case shows two issues with transaction_wrap:

1) If the original function is not transaction_safe, but the wrapper is
declared safe, this incorrectly results in an compilation error about the
original and the wrapper function being incompatible.
I believe this used to work before, but haven't checked.

2) If a wrapper is declared transaction_pure, the original function is
incorrectly considered to be transaction_pure.

The fourth case in the test might be something to be considered adding support
for.  OTOH, perhaps it's safer for programmers having to explicitly select
whether a wrapper is pure or safe, given that there seem to be these two
separate use cases (ie, making it pure to customize instrumentation, and making
it safe to use a transaction-friendly wrapper that still needs to be
instrumented).