Date: Thu, 18 Feb 1999 18:57:46 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender: eliz AT is
To: DJ Delorie <dj AT delorie DOT com>
cc: djgpp-workers AT delorie DOT com
Subject: Re: Passing FLAGS from RMCBs
In-Reply-To: <Pine.SUN.3.91.990217161556.17443F-100000@is>
Message-ID: <Pine.SUN.3.91.990218185002.8179B-100000@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Reply-To: djgpp-workers AT delorie DOT com

Here's a patch that allows to pass FLAGS back to real mode.  (The rest
of TLC required by gormcb.c will have to wait for now.)  The diffs are 
preceded by a suitable "What's new" entry.

-------------------------------------------------------------------
Real-mode callbacks set up by 
@code{_go32_dpmi_allocate_real_mode_callback_iret} no longer overwrite 
the @code{flags} member of the @code{__dpmi_regs} struct passed to the 
user-defined interrupt handler.  Thus, you can now install handlers 
which set/reset bits in the @code{flags}, and these changes will be 
passed back to real mode.
@findex _go32_dpmi_allocate_real_mode_callback_iret

*** src/libc/go32/gormcb.c~0	Sun Jun 28 22:18:54 1998
--- src/libc/go32/gormcb.c	Thu Feb 18 18:35:52 1999
*************** static unsigned char wrapper_retf[] = {
*** 74,81 ****
--- 74,86 ----
  };
  
  static unsigned char wrapper_iret[] = {
+ #if 0
+   /* This overwrote the FLAGS in the real-mode call structure with
+      their original value, thus making it impossible for the user's
+      RMCB to change FLAGS (e.g., to set/reset the carry bit).  */
           0x66, 0x8b, 0x46, 0x04,		/* mov     ax,[esi+4]      */
           0x66, 0x26, 0x89, 0x47, 0x20,		/* mov     es:[edi+32],ax  */
+ #endif
           0x66, 0x26, 0x83, 0x47, 0x2e, 0x06,	/* add     es:[edi+46],0x6 */
           0xcf					/* iret                    */
  };