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bug#39954: bug#50153: Acknowledgement (call-with-values outside tail pos
From: |
Maxime Devos |
Subject: |
bug#39954: bug#50153: Acknowledgement (call-with-values outside tail position + backtrace + compilation causes segfault) |
Date: |
Sat, 21 Aug 2021 22:17:56 +0200 |
User-agent: |
Evolution 3.34.2 |
I did some debugging on the C side, using 'rr':
LD_LIBRARY_PATH=.libs ../meta/uninstalled-env rr record ./.libs/guile
--fresh-auto-compile -l ../crash.scm
it leads to a segfault, as expected. According to #39954, which looks
similar, 'frame-local-ref' returns (SCM)0x0. So I tried some reverse debugging:
rr replay guile-3
break scm_frame_local_ref
reverse-continue
reverse-continue
I noticed "repr" was STACK_ITEM_SCM, and item->as_scm was set to 0x07
(which is invalid). On another run, it was set to 0x09 (also invalid?).
I modified scm_frame_local_ref a bit so it ignores these 0x07 and 0x09
and treats them like SCM_EOF_VAL instead. That allows printing the backtrace,
though I don't see those #<eof> appearing in the output.
Would someone know what's going on here?
Greetings,
Maxime
diff --git a/libguile/frames.c b/libguile/frames.c
index 0bb40579c..87afaec3d 100644
--- a/libguile/frames.c
+++ b/libguile/frames.c
@@ -41,6 +41,7 @@
#include "frames.h"
+#include <stdio.h>
SCM
scm_c_make_frame (enum scm_vm_frame_kind kind, const struct scm_frame *frame)
@@ -272,6 +273,11 @@ scm_frame_local_ref (SCM frame, SCM index, SCM
representation)
switch (repr)
{
case STACK_ITEM_SCM:
+ fprintf(stderr, "i: %u SCM: %p\n", (unsigned) i,
(void*)item->as_u64);
+ if (item->as_u64 == 0x07)
+ return SCM_EOF_VAL;
+ if (item->as_u64 == 0x09)
+ return SCM_EOF_VAL;
return item->as_scm;
case STACK_ITEM_F64:
return scm_from_double (item->as_f64);
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