gdb/1434: Bad calls to execl()

[brandt at fokus dot fraunhofer dot de]

>Number:         1434
>Category:       gdb
>Synopsis:       Bad calls to execl()
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Oct 30 14:08:01 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     Harti Brandt
>Release:        6.0 and prior
>Organization:
>Environment:
Any
>Description:
The gdb source contains several calls to execl of the following forms:

   execl(...., 0)
or
   execl(...., NULL)

Both of these calls invoke undefined behaviour according to
ISO-C. The problem is, that for a variadic function the compile will do only default promotions so in both cases an
integer 0 will be passed to the function (unless on the concrete OS NULL is defined as (void *)0 which is not required by the standard). execl() expectes a null pointer to terminate the argument list. In order to pass a null pointer one has to explicitely cast the 0 or null pointer constant (NULL) to a pointer type:

  execl(...., (char *)NULL)

While the bad call usually makes no difference on systems
where sizeof(int) != sizeof(char *) it breaks badly on
systems where this is not true.
>How-To-Repeat:

>Fix:
Apply the attached patch
>Release-Note:
>Audit-Trail:
>Unformatted:
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