[syslinux] argv[0] doesn't contain module name and cat.c32 hangs with Syslinux 4.00-pre36

[Gert Hulselmans]

The program name of the module can't be retrieved with argv[0].
I tested it by running cat.c32 (com32/samples/cat.c32).
In Syslinux 3.85, argv[0] returns an empty string.
In Syslinux 4.00-pre36, argv[0] returns some garbage characters.


ISOLINUX 3.85 2010-02-20 ETCD Copyright (C) 1994-2010 H. Peter Anvin et al
argv = 0x00182c44
argv[0] = 0x07fbffc3 = ""
argv[1] = 0x00182c34 = "isolinux.cfg"
argv[2] = 0x00000000 = "(null)"
File = isolinux.cfg
DEFAULT cat_file

LABEL cat_file
COM32 cat.c32
APPEND isolinux.cfg

boot:


EXTLINUX 4.00 4.00-pre36  Copyright (C) 1994-2010 H. Peter Anvin et al
Press 1 to see the menu
Hello, World! from (hello.c)
argv = 0x001e1e48
argv[0] = 0x07fdffbf = "�"
argv[1] = 0x001e1e38 = "extlinux.conf"
argv[2] = 0x00000000 = "(null)"
File = extlinux.conf
DEFAULT cat_file

LABEL cat_file
COM32 cat.c32
APPEND extlinux.conf

boot:



On my PC, cat.c32 (com32/samples/cat.c32) of Syslinux 4.00-pre36 hangs when
you specify a file that doesn't exist (works fine in kvm).
It works fine with Syslinux 3.85.

Checking if the file exist, before trying to read its contents, fixes the
issue.
I also replace "exit(1)" by "return 1;" (suggestion of Shao Miller).


$ diff -up syslinux-4.00-pre36-original/com32/samples/cat.c
syslinux-4.00-pre36/com32/samples/cat.c
--- syslinux-4.00-pre36-original/com32/samples/cat.c	2010-03-07
00:13:36.000000000 +0100
+++ syslinux-4.00-pre36/com32/samples/cat.c	2010-03-18 18:02:58.499575668
+0100

@@ -15,13 +15,18 @@ int main(int argc, char *argv[])
 	printf("argv[%d] = %p = \"%s\"\n", i, argv[i], argv[i]);

     if (argc < 2) {
-	fprintf(stderr, "Missing file name!\n");
-	exit(1);
+	fprintf(stderr, "Usage: cat.c32 filename\n");
+	return 1;
     }

     printf("File = %s\n", argv[1]);

     f = fopen(argv[1], "r");
+    if (!f) {
+	fprintf(stderr, "File name \"%s\" does not exist.\n", argv[1]);
+	return 1;
+    }
+
     while ((ch = getc(f)) != EOF)
 	putchar(ch);


Also a true cat.c32 module would be nice to have.
So a cat.c32 module that doesn't display this part:
===================================================
argv = 0x001e1e48
argv[0] = 0x07fdffbf = "�"
argv[1] = 0x001e1e38 = "extlinux.conf"
argv[2] = 0x00000000 = "(null)"
File = extlinux.conf
===================================================

Maybe replacing strange characters with "?" would even be better.
A more.c32 module would also be useful.

$ cat com32/modules/cat.c
#include <stdio.h>
#include <stdlib.h>
#include <console.h>

int main(int argc, char *argv[])
{
    FILE *f;
    int ch;

    openconsole(&dev_stdcon_r, &dev_stdcon_w);

    if (argc != 2) {
	fprintf(stderr, "Usage: cat.c32 filename\n");
	return 1;
    }

    f = fopen(argv[1], "r");
    if (!f) {
	fprintf(stderr, "File name \"%s\" does not exist.\n", argv[1]);
	return 1;
    }

    while ((ch = getc(f)) != EOF)
	putchar(ch);

    fclose(f);

    return 0;
}


- Gert Hulselmans