save si_stack_hwm across JMPENV_PUSH
authorDavid Mitchell <davem@iabyn.com>
Mon, 3 Jul 2017 12:43:27 +0000 (13:43 +0100)
committerDavid Mitchell <davem@iabyn.com>
Mon, 3 Jul 2017 12:43:27 +0000 (13:43 +0100)
When continuing after an exception (JMPENV_PUSH() returns 3),
restore the value of PL_curstackinfo->si_stack_hwm.

This is a recently added variable on debugging builds that detects
attempts to push stuff on the stack without extending it.
After an exception  its value may be invalid and trigger a false panic.

cop.h

diff --git a/cop.h b/cop.h
index 2be8fb1..be23b3d 100644 (file)
--- a/cop.h
+++ b/cop.h
@@ -35,10 +35,25 @@ struct jmpenv {
     int                        je_ret;         /* last exception thrown */
     bool               je_mustcatch;   /* need to call longjmp()? */
     U16                 je_old_delaymagic; /* saved PL_delaymagic */
+#if defined DEBUGGING && !defined DEBUGGING_RE_ONLY
+    SSize_t             je_old_stack_hwm;
+#endif
 };
 
 typedef struct jmpenv JMPENV;
 
+#if defined DEBUGGING && !defined DEBUGGING_RE_ONLY
+#  define JE_OLD_STACK_HWM_zero      PL_start_env.je_old_stack_hwm = 0
+#  define JE_OLD_STACK_HWM_save(je)  \
+        (je).je_old_stack_hwm = PL_curstackinfo->si_stack_hwm
+#  define JE_OLD_STACK_HWM_restore(je)  \
+        PL_curstackinfo->si_stack_hwm = (je).je_old_stack_hwm
+#else
+#  define JE_OLD_STACK_HWM_zero        NOOP
+#  define JE_OLD_STACK_HWM_save(je)    NOOP
+#  define JE_OLD_STACK_HWM_restore(je) NOOP
+#endif
+
 /*
  * How to build the first jmpenv.
  *
@@ -57,6 +72,7 @@ typedef struct jmpenv JMPENV;
        PL_start_env.je_ret = -1;               \
        PL_start_env.je_mustcatch = TRUE;       \
        PL_start_env.je_old_delaymagic = 0;     \
+        JE_OLD_STACK_HWM_zero;                  \
     } STMT_END
 
 /*
@@ -102,7 +118,9 @@ typedef struct jmpenv JMPENV;
            Perl_deb(aTHX_ "JUMPENV_PUSH level=%d at %s:%d\n",          \
                         i,  __FILE__, __LINE__);})                     \
        cur_env.je_prev = PL_top_env;                                   \
+        JE_OLD_STACK_HWM_save(cur_env);                                 \
        cur_env.je_ret = PerlProc_setjmp(cur_env.je_buf, SCOPE_SAVES_SIGNAL_MASK);              \
+        JE_OLD_STACK_HWM_restore(cur_env);                              \
        PL_top_env = &cur_env;                                          \
        cur_env.je_mustcatch = FALSE;                                   \
        cur_env.je_old_delaymagic = PL_delaymagic;                      \