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On Saturday, December 16th, 2023 at 11:26 AM, American Citizen
<[email protected]> wrote:
> Hello:
>
> I bumped into a curious problem with the argv variables changing, when a
> certain file named "1" is added into the local directory of the executable.
>
> Here is the test file, a simple program named test.c
>
> > #include <stdio.h>
> > #include <string.h>
> >
> > int main(int argc, char **argv) {
> >
> > int i=1;
> > //int STDIN = 1;
> >
> > char INCURV[1024] = {'\0'};
> >
> > while(i<argc) {
> > if (!strcmp(argv[i],"-curve")) {
> > printf("we are here \n");
> > //strcpy(INCURV,argv[i+1]); STDIN=0; i+=2;
> > }
> > i+=1;
> > }
> > return 0;
> > }
>
> I compile this file as
>
> % gcc -o wack test.c -ggdb
>
> (it is too easy to wipe out the source file if the object name almost
> matches)
>
> gcc is gcc version 7.5.0 (SUSE Linux)
>
> I have the gdb debugger stop on line 13 "printf("we are here\n");"
>
> Using input to the command:
>
> % wack -arderivs -curve [0,0,0,-1156,0]
>
> when no file named "1" exists in the directory then argv looks okay
>
> argv[0] = "/../../wack"
>
> argv[1] = "-arderivs"
>
> argv[2] = "-curve"
>
> argv[3] = "[0,0,0,-1156,0]"
>
> argv[4] = 0x0
>
> which is all fine and well.
>
> I used the touch command to create file "1" in the local directory
>
> % touch 1
>
> and restart the gdb debugger.
>
> argc count = 4 as expected
>
> but argv[3] = "1"
>
> Is this a bug in c?
>
> Why is argv[3] changed?
It's a shell issue, not a C issue. The shell is interpreting something in the
square-bracketed argument as special characters. To avoid it, put the argument
in quotes.
(gdb) r -arderivs -curve 1
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /tmp/wack -arderivs -curve 1
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
Demo:
(gdb) r -arderivs -curve [0,0,0,-1156,0]
...
Breakpoint 1, main (argc=4, argv=0x7fffffffd568) at test.c:6
6 int i=1;
(gdb) p argv[3]
$8 = 0x7fffffffd99f "1"
(gdb) r -arderivs -curve "[0,0,0,-1156,0]"
...
Breakpoint 1, main (argc=4, argv=0x7fffffffd558) at test.c:6
6 int i=1;
(gdb) p argv[3]
$9 = 0x7fffffffd991 "[0,0,0,-1156,0]"
>
> Randall
