points. For library functions, the pattern is __sleep() <--
_libc_sleep() <-- sleep(). The arrows represent weak aliases. For
system calls, the pattern is _read() <-- _libc_read() <-- read().
that counted the number of elements in argv. The counter is incremented
in the next-iteration section of the loop, not the body, so at termination
it's already "counted" the element that failed the continuation test - in
this case the NULL argv terminator.
Noted by: bde
call them. All the execX() libc functions should be vfork() safe now.
Specifically:
- execlp() does the argument count-and-build into a vector from alloca
(like the others) - buildargv() is no longer used (and gone).
- execvp() uses alloca/strcpy rather than strdup().
- the ENOEXEC handler uses alloca rather than malloc.
- a couple of free() calls removed - alloca works on the local stack and
the allocations are freed on function exit (which is why buildargv
wasn't useful - it's alloca() context would disappear on return).
Along the way:
- If alloca() fails (can it?), set errno = ENOMEM explicitly.
- The ENOEXEC recovery routine that trys again with /bin/sh appeared to
not be terminating the new argv[] array for /bin/sh, allowing it to
walk off the end of the list.
I dithered a bit about using alloca() even more as it's most commonly
associated with gcc. However, standalone portable (using malloc) and
machine-specific assembler alloca implementations appear to be available
on just about all the architectures we're likely to want to port to.
alloca will be the least of our problems if ever going to another compiler.
to POSIX.2. In particular:
- don't retry for ETXTBSY. This matches what sh(1) does. The retry code
was broken anyway. It only slept for several seconds for the first few
retries. Then it retried without sleeping.
- don't abort the search for errors related to the path prefix, in
particular for ENAMETOOLONG, ENOTDIR, ELOOP. This fixes PR1487. sh(1)
gets this wrong in the opposite direction by never aborting the search.
- don't confuse EACCES for errors related to the path prefix with EACCES
for errors related to the file. sh(1) gets this wrong.
- don't return a stale errno when the search terminates normally without
finding anything. The errno for the last unsuccessful execve() was
usually returned. This gave too much precedence to pathologies in the
last component of $PATH. This bug is irrelevant for sh(1).
The implementation still uses the optimization/race-inhibitor of trying
to execve() things first. POSIX.2 seems to require looking at file
permissions using stat(). We now use stat() after execve() if execve()
fails with an ambiguous error. Trying execve() first may actually be a
pessimization, since failing execve()s are fundamentally a little slower
than stat(), and are significantly slower when a file is found but has
unsuitable permissions or points to an unsuitable interpreter.
PR: 1487
Garbage in `eacces' caused the wrong errno to be set for non-EACCES errors.
Garbage in `etxtbsy' caused a semi-random retry strategy for ETXTBSY errors.
Found by: NIST-PCTS. gcc -Wall reported the problem, but -Wall is not
enabled for libc.
pointer returned by realloc(). All callers free the pointer if the
execve fails. Nuke the caching. This essentially restores buildargv()
to the 1.1.5 version. Also fix a memory leak if realloc() fails. Also
nuke similar but non-broken caching in execvp(). malloc() should be
efficient enough.
