STD before DragQueryFile returns wrong results

[Igor]

When I use STD (set direction flag) before calling DragQueryFile it will always return 1 for number of characters in a file path, which of course is not correct.

Is this a bug or do I have to clear the flag before calling any windows api functions?


This is with 64bit code, don't know if its the same for 32bit code.

[dedndave]

if you set the direction flag, you should clear it prior to calling an API
if the state needs to be preserved across the call, it's PUSHF/POPF
CLD, STD, PUSHF, POPF are surprisongly slow instructions - but that may not matter where you are using them

[Igor]

if you set the direction flag, you should clear it prior to calling an API

Thanks, didn't know that :)

[Rockoon]

The STDCALL calling convention defines the rule:

"the direction flag is clear on entry and must be returned clear."

[hutch--]

Long ago I learnt that if you use instructions that depend on the direction flag, set it yourself and make sure on exit that it is clear.