Fix SAFE_ALLOCA to not exhaust the stack when in a loop.

Problem reported by Dmietry Antipov in thread leading to:
http://lists.gnu.org/archive/html/emacs-devel/2014-09/msg00713.html
This patch fixes only SAFE_ALLOCA, SAFE_NALLOCA, and SAFE_ALLOCA_LISP;
the experimental local_* macros enabled by USE_LOCAL_ALLOCATORS
remain unfixed.
* callproc.c (call_process): Save and restore sa_avail.
* lisp.h (USE_SAFE_ALLOCA): Define sa_avail.
(AVAIL_ALLOCA): New macro.
(SAFE_ALLOCA, SAFE_NALLOCA, SAFE_ALLOCA_LISP):
Use it, and check against sa_avail rather than MAX_ALLOCA.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/callproc.c b/src/callproc.c
index 798f441bdef..4bedf671e83 100644
--- a/src/callproc.c
+++ b/src/callproc.c
@@ -632,6 +632,7 @@ call_process (ptrdiff_t nargs, Lisp_Object *args, int filefd,
     int volatile fd_error_volatile = fd_error;
     int volatile filefd_volatile = filefd;
     ptrdiff_t volatile count_volatile = count;
+    ptrdiff_t volatile sa_avail_volatile = sa_avail;
     ptrdiff_t volatile sa_count_volatile = sa_count;
     char **volatile new_argv_volatile = new_argv;
     int volatile callproc_fd_volatile[CALLPROC_FDS];
@@ -648,6 +649,7 @@ call_process (ptrdiff_t nargs, Lisp_Object *args, int filefd,
     fd_error = fd_error_volatile;
     filefd = filefd_volatile;
     count = count_volatile;
+    sa_avail = sa_avail_volatile;
     sa_count = sa_count_volatile;
     new_argv = new_argv_volatile;