top: exploit msg handler override to avoid corrupt tty

Way back in November of 2011, the library was equipped
with an overridable error message handler function. It
was done expressly for a program like top which alters
the tty. But that support was withdrawn shortly after.

This was all done in the lead up to v3.3.2. That's the
release where NLS support was added and it represented
a hectic time. In hindsight, the changes went too far.

So this commit, in a minimal fashion, restores ability
to address a potential fatal library error. After all,
any properly behaving library would never unilaterally
subject a caller to a stderr message and then an exit.

[ when exposing 1 variable in libprocps.sym, 2 other ]
[ existing symbols were repositioned alphabetically. ]

Reference(s):
. generalized library memory provisions
commit 7126cc4491
. top exploit library memory provisions
commit 88087ec5a5
. library xalloc type functions made private
commit 2865ded64e
. restored prior top memory logic
commit 05f5deb97c

Signed-off-by: Jim Warner <james.warner@comcast.net>

proc/libprocps.sym

@@ -47,7 +47,9 @@ global:
 	page_bytes;
 	pretty_print_signals;
 	print_uptime;
+	procps_linux_version;
 	put_slabinfo;
+	pwcache_get_user;
 	readeither;
 	readproc;
 	readproctab2;
@@ -62,8 +64,7 @@ global:
 	tty_to_dev;
 	unix_print_signals;
 	uptime;
-	pwcache_get_user;
+	xalloc_err_handler;
-	procps_linux_version;
 local:
 	*;
 };

top/top.c

@@ -47,6 +47,7 @@
 #include "../include/fileutils.h"
 #include "../include/nls.h"
 
+#include "../proc/alloc.h"
 #include "../proc/devname.h"
 #include "../proc/numa.h"
 #include "../proc/procps.h"
@@ -640,6 +641,20 @@ static void sig_resize (int dont_care_sig) {
    Frames_signal = BREAK_sig;
    (void)dont_care_sig;
 } // end: sig_resize
+
+
+        /*
+         * Handles libproc memory errors, so our tty can be reset */
+static void xalloc_our_handler (const char *fmts, ...) {
+   static char buf[MEDBUFSIZ];
+   va_list va;
+
+   va_start(va, fmts);
+   vsnprintf(buf, sizeof(buf), fmts, va);
+   va_end(va);
+   scat(buf, "\n");
+   bye_bye(buf);
+} // end: xalloc_our_handler
 
 /*######  Special UTF-8 Multi-Byte support  ##############################*/
 
@@ -3465,6 +3480,9 @@ static void before (char *me) {
    // accommodate nls/gettext potential translations
    initialize_nls();
 
+   // override default library memory alloc error handler
+   xalloc_err_handler = xalloc_our_handler;
+
    // establish cpu particulars
 #ifdef PRETEND8CPUS
    smp_num_cpus = 8;

top/top.h

@@ -681,6 +681,7 @@ typedef struct WIN_t {
 //atic void          sig_endpgm (int dont_care_sig);
 //atic void          sig_paused (int dont_care_sig);
 //atic void          sig_resize (int dont_care_sig);
+//atic void          xalloc_our_handler (const char *fmts, ...);
 /*------  Special UTF-8 Multi-Byte support  ------------------------------*/
 /*atic char          UTF8_tab[] = { ... }                                 */
 //atic int           utf8_delta (const char *str);