From: Keith.S.Thompson+u@gmail.com   
      
   Michael Sanders  writes:   
   > On Tue, 30 Dec 2025 18:42:30 GMT, Scott Lurndal wrote:   
   >> What if 'argv[0]' is NULL (and argc == 0)?   
   >   
   > Well, seems we have to make a choice, ISO vs. POSIX:   
   >   
   > *ISO C (C17 / C23)*:   
   >   
   > C17, 5.1.2.2.1 "Program startup"   
   >   
   > The value of argc shall be nonnegative.   
   >   
   > argv[argc] shall be a null pointer.   
      
   [...]   
      
   > *POSIX.1-2017 (and later)*   
   >   
   > POSIX execve() specification:   
   >   
   > The argument argv is an array of character pointers   
   > to null-terminated strings.   
   >   
   > The application shall ensure that argv[0] points to a filename   
   > string that is associated with the process being started.   
      
   [...]   
      
   > What say you?   
      
   It happens that I recently spent some time looking into this.   
      
   As you say, POSIX requires argc >= 1, but ISO C only guarantees   
   argc >= 0.   
      
   If argc == 0, a program that assumes argv[0] is non-null   
   can run into serious problems if that assumption is invalid.   
   In particular, a program called "pkexec" would try to traverse   
   arguments starting with argv[1], which logically doesn't   
   exist if argc==0.  Due to the way program arguments are laid   
   out in memory, argv[1] is also envp[0].  Frivolity ensued.   
   See .   
      
   The Linux kernel updated execve to ensure that the invoked program   
   has argc>=1.  It was patched in early 2022.  NetBSD still has this   
   vulnerability.   
      
   Summary: Some systems guarantee that argc>=1 and argv[0] points to   
   a valid string, but software that's intended to be portable should   
   tolerate argc==0 and argv[0]==NULL.   
      
   For more information, see   
   .   
      
   --   
   Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com   
   void Void(void) { Void(); } /* The recursive call of the void */   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)