DOS ain't dead

Hello,

Regarding https://www.fourmilab.ch/onetime/otp-1.2.2.tar.gz

Using DJGPP under Windows I was able to compile it for Win32 target without any problems.

Using equivalent DOS DJGPP build on the same source code all I produced was a long screen of compiler rants about various errors, some with suggestions of fixes based on various "-W" directives, but they were not helpful, because program does not compile, even if some of the errors vanished.

So how to compile this code for DOS (32 bit) target? Please note I am not fluent in C.

---
echo g=ffff:0|debug>nul

If you patch it like the following, it does compile.
(Not run-tested at all, though.)


--- otp.c~
+++ otp.c
@@ -55,8 +55,12 @@
 #ifdef WIN32
 #include <windows.h>
 #endif
-
-#ifdef unix
+#ifdef __DJGPP
+#define __far
+#define _intdos intdos
+#define _REGS REGS
+#endif
+#if defined(unix) && !defined(__DJGPP)
 #include <sys/time.h>
 extern int getpid(), getppid(), gethostid();
 #endif
@@ -189,7 +193,7 @@
 #ifdef MSDOS
     union _REGS ri, ro;
 #endif
-#ifdef unix
+#if defined(unix) && !defined(__DJGPP)
     struct timeval tv;
 #endif
     
@@ -340,7 +344,7 @@
 #define OS_KNOWN 1
 #endif
 
-#ifdef unix
+#if defined(unix) && !defined(__DJGPP)
     FILE *rf;
     size_t ct;


patch.exe from UnxUtils failed, same for patch.exe from Perl for Windows.

Error message:

patching file otp.c
Hunk #2 FAILED at 193.
patch unexpectedly ends in middle of line
Hunk #3 succeeded at 344 with fuzz 2.
1 out of 3 hunks FAILED -- saving rejects to file otp.c.rej


otp.c.rej contents:

***************
*** 189,195 ****
  #ifdef MSDOS
      union _REGS ri, ro;
  #endif
- #ifdef unix
      struct timeval tv;
  #endif
     
--- 193,199 ----
  #ifdef MSDOS
      union _REGS ri, ro;
  #endif
+ #if defined(unix) && !defined(__DJGPP)
      struct timeval tv;
  #endif
     

> If you patch it like the following, it does compile.
> (Not run-tested at all, though.)
>
>
> --- otp.c~
> +++ otp.c
> @@ -55,8 +55,12 @@
> #ifdef WIN32
> #include <windows.h>
> #endif
> -
> -#ifdef unix
> +#ifdef __DJGPP
> +#define __far
> +#define _intdos intdos
> +#define _REGS REGS
> +#endif
> +#if defined(unix) && !defined(__DJGPP)
> #include <sys/time.h>
> extern int getpid(), getppid(), gethostid();
> #endif
> @@ -189,7 +193,7 @@
> #ifdef MSDOS
> union _REGS ri, ro;
> #endif       
> -#ifdef unix
> +#if defined(unix) && !defined(__DJGPP)
> struct timeval tv;
> #endif
>
> @@ -340,7 +344,7 @@
> #define OS_KNOWN 1
> #endif
>
> -#ifdef unix
> +#if defined(unix) && !defined(__DJGPP)
> FILE *rf;
> size_t ct;
>

---
echo g=ffff:0|debug>nul

Hello rosegondon, hello sezeros,

> patching file otp.c
> Hunk #2 FAILED at 193.
> patch unexpectedly ends in middle of line
> Hunk #3 succeeded at 344 with fuzz 2.
> 1 out of 3 hunks FAILED -- saving rejects to file otp.c.rej
>

Whitespace issue (argh!). There is a tab character after the first #endif in the rejected patch portion --- you will need to edit the patch to add it in (or maybe change spaces into tabs).

Actually I think sezeros's patch throws away a bit too much code. The Unix-specific code (#ifdef unix ... #endif) tries to gather some bits of randomness by calling gettimeofday(...):

#ifdef unix
    FILE *rf;
    size_t ct;
   
        gettimeofday(&tv, (struct timezone *) NULL);
        trash[1] = tv.tv_sec;
        trash[2] = tv.tv_usec;
        ...
#define OS_KNOWN 1
#endif

... and DJGPP does support gettimeofday(...). Unfortunately, the patch will disable the code, which will reduce the amount of randomness the program can use. There is probably a better way...

Thank you!

---
https://gitlab.com/tkchia · https://codeberg.org/tkchia · 😴 "MOV AX,0D500H+CMOS_REG_D+NMI"

Hello rosegondon,

My proposed modified patch (for now) is as follows:

--- otp.c.orig    2021-09-18 18:49:22.723186562 +0000
+++ otp.c       2021-09-18 19:27:31.893487497 +0000
@@ -57,4 +57,10 @@
 #endif
 
+#ifdef __DJGPP
+#define __far
+#define _intdos intdos
+#define _REGS REGS
+#endif
+
 #ifdef unix
 #include <sys/time.h>
@@ -311,8 +317,8 @@
        ri.h.dl = 0;            /* Default drive */
        if (_intdos(&ri, &ro) != 0xFFFF) {
-           trash[1] = (((int32_t) ro.x.ax) << 16) | ro.x.bx;
-           trash[2] = (((int32_t) ro.x.cx) << 16) | ro.x.dx;
+           trash[5] = (((int32_t) ro.x.ax) << 16) | ro.x.bx;
+           trash[6] = (((int32_t) ro.x.cx) << 16) | ro.x.dx;
        }
-       trash[4] = (int32_t) (char __far *) trash;
+       trash[7] = (int32_t) (char __far *) trash;
 #define OS_KNOWN 1
 #endif
@@ -353,5 +359,7 @@
        trash[4] = getpid();
        trash[11] = getppid();
+#ifndef __DJGPP
        trash[38] = gethostid();
+#endif
        /* If the system implements /dev/random, obtain 16 bytes
           of entropy thence. */

Further improvements are probably possible.

Thank you!

---
https://gitlab.com/tkchia · https://codeberg.org/tkchia · 😴 "MOV AX,0D500H+CMOS_REG_D+NMI"

Hi sezeroz & tkchia,

@sezeroz, thank you for your patch, after I applied it, program compiled regardless of patching errors.

@tkchia, your patch triggers whitespace errors too, I will try to
manually apply your modifications in source code. Probably something happens with text when copying&pasting from this forum to patch file.

Thank you for you help, now I will make code changes and tests on my DOS machine and I hope to come back with results soon.

> Hello rosegondon,
>
> My proposed modified patch (for now) is as follows:
>
> --- otp.c.orig    2021-09-18 18:49:22.723186562 +0000
> +++ otp.c  2021-09-18 19:27:31.893487497 +0000
> @@ -57,4 +57,10 @@
> #endif
>
> +#ifdef __DJGPP
> +#define __far
> +#define _intdos intdos
> +#define _REGS REGS
> +#endif
> +
> #ifdef unix
> #include <sys/time.h>
> @@ -311,8 +317,8 @@
> ri.h.dl = 0;               /* Default drive */
> if (_intdos(&ri, &ro) != 0xFFFF) {
> -          trash[1] = (((int32_t) ro.x.ax) << 16) | ro.x.bx;
> -      trash[2] = (((int32_t) ro.x.cx) << 16) | ro.x.dx;
> +     trash[5] = (((int32_t) ro.x.ax) << 16) | ro.x.bx;
> +      trash[6] = (((int32_t) ro.x.cx) << 16) | ro.x.dx;
> }
> -      trash[4] = (int32_t) (char __far *) trash;
> +  trash[7] = (int32_t) (char __far *) trash;
> #define OS_KNOWN 1
> #endif
> @@ -353,5 +359,7 @@
> trash[4] = getpid();
> trash[11] = getppid();
> +#ifndef __DJGPP
> trash[38] = gethostid();
> +#endif
> /* If the system implements /dev/random, obtain 16 bytes
> of entropy thence. */
>
> Further improvements are probably possible.
>
> Thank you!

---
echo g=ffff:0|debug>nul

> @tkchia, your patch triggers whitespace errors too, I will try to
> manually apply your modifications in source code. Probably something
> happens with text when copying&pasting from this forum to patch file.

The Linux manual for patch says this (which was what I faintly remembered):

> -l or --ignore-whitespace
> Match patterns loosely, in case tabs or spaces have been
> munged in your files. Any sequence of one or more blanks in
> the patch file matches any sequence in the original file, and
> sequences of blanks at the ends of lines are ignored. Normal
> characters must still match exactly. Each line of the context
> must still match a line in the original file.

@Rugxulo, thank you! After using this directive patches were applied without errors.

> > @tkchia, your patch triggers whitespace errors too

> > -l or --ignore-whitespace
> > Match patterns loosely, in case tabs or spaces have been
> > munged in your files.

---
echo g=ffff:0|debug>nul