Win32 GetMessage: The BOOL That Returns Nonzero, Zero, or -1

Description

A dark-themed screenshot of Microsoft's Win32 API documentation for the GetMessage function's 'Return value' section. It states the type is 'BOOL' (highlighted), then explains: if the function retrieves a message other than WM_QUIT, the return value is nonzero; if it retrieves the WM_QUIT message, the return value is zero; if there is an error, the return value is -1 - for example if hWnd is an invalid window handle or lpMsg is an invalid pointer, with GetLastError for extended info. The final line, with 'the return value can be nonzero, zero, or -1' highlighted, reads 'Because the return value can be nonzero, zero, or -1, avoid code like this:'. The humor is the self-evident absurdity of a 'boolean' type with three meaningful states, a legendary Win32 API design wart that has caused countless message-loop bugs from 'while (GetMessage(...))' patterns

Common Tags

API ApplicationProgrammingInterface Windows TechnicalDocumentation WindowsDevelopment BackwardCompatibility TypeSystems Microsoft ErrorHandling BooleanLogic

Comments

Anonymous ★ Top Pick Win32's BOOL has three values because backwards compatibility means never having to say your type system is sorry

Anonymous ★ Top Pick

Win32's BOOL has three values because backwards compatibility means never having to say your type system is sorry
Anonymous

It's a `BOOL`; the third truth value is 'check GetLastError, coward.'
@TheFloofyFloof 5mo

technically valid
@gremion_cto 5mo

Winapi vibes
1. @SamsonovAnton 5mo
  
  WomenAPI vibes, where "yes" may as well have a negative meaning, and "no" may be an acknowledgement ("no problem"). 💅
@gremion_cto 5mo

Yeah! I was right! https://github.com/microsoft/CsWin32/issues/362
@deadgnom32 5mo

but -1 IS nonzero
1. @blue_bonsai 5mo
  
  Shhhhh don't break it down to them.
Егор 5mo

zoomers discovered winapi BOOL is not boolean typedef int BOOL;
@sysoevyarik 5mo

>tristate Phineas and ferb ahh programming
@blue_bonsai 5mo

What
@b7sum 5mo

whar.
@azizhakberdiev 5mo

I find it stupid how we have a 1 bit type when all machines are 8 bit addressible
1. @purplesyringa 5mo
  
  bool is useful as an abstraction, not as a fixed-width type