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authorBjörn Gustavsson <[email protected]>2011-03-08 13:16:05 +0100
committerBjörn Gustavsson <[email protected]>2011-08-16 08:58:50 +0200
commit61e4c1626ba1f2357cf803f4e99352fd73d925d0 (patch)
treee9ca4d24e7ab82044aac3d25aa6084acff773d51
parent71fa3d0011cc19236de082ae068ed2306774e91a (diff)
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Fix decrement of continuation pointers
-rw-r--r--erts/emulator/beam/beam_emu.c27
1 files changed, 23 insertions, 4 deletions
diff --git a/erts/emulator/beam/beam_emu.c b/erts/emulator/beam/beam_emu.c
index 3c323634b7..a7d7e851cf 100644
--- a/erts/emulator/beam/beam_emu.c
+++ b/erts/emulator/beam/beam_emu.c
@@ -5687,6 +5687,25 @@ expand_error_value(Process* c_p, Uint freason, Eterm Value) {
* that c_p->ftrace will point to a cons cell which holds the given args
* and the saved data (encoded as a bignum).
*
+ * There is an issue with line number information. Line number
+ * information is associated with the address *before* an operation
+ * that may fail or be stored stored on the stack. But continuation
+ * pointers point after its call instruction, not before. To avoid
+ * finding the wrong line number, we'll need to adjust them so that
+ * they point at the beginning of the call instruction or inside the
+ * call instruction. Since its impractical to point at the beginning,
+ * we'll do the simplest thing and decrement the continuation pointers
+ * by one.
+ *
+ * Here is an example of what can go wrong. Without the adjustment
+ * of continuation pointers, the call at line 42 below would seem to
+ * be at line 43:
+ *
+ * line 42
+ * call ...
+ * line 43
+ * gc_bif ...
+ *
* (It would be much better to put the arglist - when it exists - in the
* error value instead of in the actual trace; e.g. '{badarg, Args}'
* instead of using 'badarg' with Args in the trace. The arglist may
@@ -5753,7 +5772,7 @@ save_stacktrace(Process* c_p, BeamInstr* pc, Eterm* reg, BifFunction bf,
}
/* Save second stack entry if CP is valid and different from pc */
if (depth > 0 && c_p->cp != 0 && c_p->cp != pc) {
- s->trace[s->depth++] = c_p->cp;
+ s->trace[s->depth++] = c_p->cp - 1;
depth--;
}
s->pc = NULL;
@@ -5773,13 +5792,13 @@ save_stacktrace(Process* c_p, BeamInstr* pc, Eterm* reg, BifFunction bf,
/* Save first stack entry */
ASSERT(c_p->cp);
if (depth > 0) {
- s->trace[s->depth++] = c_p->cp;
+ s->trace[s->depth++] = c_p->cp - 1;
depth--;
}
s->pc = NULL; /* Ignore pc */
} else {
if (depth > 0 && c_p->cp != 0 && c_p->cp != pc) {
- s->trace[s->depth++] = c_p->cp;
+ s->trace[s->depth++] = c_p->cp - 1;
depth--;
}
s->pc = pc;
@@ -5835,7 +5854,7 @@ save_stacktrace(Process* c_p, BeamInstr* pc, Eterm* reg, BifFunction bf,
if (cp != prev) {
/* Record non-duplicates only */
prev = cp;
- s->trace[s->depth++] = cp;
+ s->trace[s->depth++] = cp - 1;
depth--;
}
ptr++;