ntdll: Fix SIGTRAP handling

[Alexandre Julliard]

Petr Tesarik <hat at tesarici.cz> writes:

> 2. The x86 spec states that a single-step interrupt (INT 1) is
>    generated if the TF bit was set when the execution of the
>    instruction BEGAN.  This means that if the instruction changes the
>    TF bit (e.g. popf), there is an INT 1, but the TF bit is not set
>    any more.  The only way to check whether the interrupt was
>    generated because of the TF bit, is to check bit 15 in DR6.

I don't see why you can't still check the TF bit, it will be set 99%
of the time, and fetching the DR6 register is quite expensive.

> The following patch fixes all of these issues.

I'd really like to see test cases showing that Windows does things
this way.

-- 
Alexandre Julliard
julliard at winehq.org