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author | Eli Zaretskii <eliz@gnu.org> | 2016-10-14 22:52:46 +0300 |
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committer | Eli Zaretskii <eliz@gnu.org> | 2016-10-14 22:52:46 +0300 |
commit | 10835b18cdfd93442e6fae093ffd130587006fcf (patch) | |
tree | 98bdfa191e4c2de8b27dbc27e2c6ef2acb17a4b4 /src | |
parent | 4de671d844c56d70e747366657664c8d293fe2bf (diff) | |
download | emacs-10835b18cdfd93442e6fae093ffd130587006fcf.tar.gz |
Avoid crashes due to objects read with the #n=object form
* src/lread.c (read1): Use Fcons for 'placeholder', not AUTO_CONS,
because elements of the list in 'read_objects' cannot be allocated
off the stack. (Bug#24640)
Diffstat (limited to 'src')
-rw-r--r-- | src/lread.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/src/lread.c b/src/lread.c index ef58b20070d..8a368806e15 100644 --- a/src/lread.c +++ b/src/lread.c @@ -2845,7 +2845,18 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list) if (c == '=') { /* Make a placeholder for #n# to use temporarily. */ - AUTO_CONS (placeholder, Qnil, Qnil); + /* Note: We used to use AUTO_CONS to allocate + placeholder, but that is a bad idea, since it + will place a stack-allocated cons cell into + the list in read_objects, which is a + staticpro'd global variable, and thus each of + its elements is marked during each GC. A + stack-allocated object will become garbled + when its stack slot goes out of scope, and + some other function reuses it for entirely + different purposes, which will cause crashes + in GC. */ + Lisp_Object placeholder = Fcons (Qnil, Qnil); Lisp_Object cell = Fcons (make_number (n), placeholder); read_objects = Fcons (cell, read_objects); |