From f9b6b37cf65c4f65c4ad461d439fbf624c0f10c1 Mon Sep 17 00:00:00 2001 From: Colin Hogben Date: Mon, 31 Oct 2016 14:05:56 +0000 Subject: [PATCH] py: Fix wrong assumption that m_renew will not move if shrinking In both parse.c and qstr.c, an internal chunking allocator tidies up by calling m_renew to shrink an allocated chunk to the size used, and assumes that the chunk will not move. However, when MICROPY_ENABLE_GC is false, m_renew calls the system realloc, which does not guarantee this behaviour. Environments where realloc may return a different pointer include: (1) mbed-os with MBED_HEAP_STATS_ENABLED (which adds a wrapper around malloc & friends; this is where I was hit by the bug); (2) valgrind on linux (how I diagnosed it). The fix is to call m_renew_maybe with allow_move=false. --- py/parse.c | 5 +++-- py/qstr.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/py/parse.c b/py/parse.c index 5920828fe9..397d46d9f0 100644 --- a/py/parse.c +++ b/py/parse.c @@ -1010,9 +1010,10 @@ mp_parse_tree_t mp_parse(mp_lexer_t *lex, mp_parse_input_kind_t input_kind) { // truncate final chunk and link into chain of chunks if (parser.cur_chunk != NULL) { - (void)m_renew(byte, parser.cur_chunk, + (void)m_renew_maybe(byte, parser.cur_chunk, sizeof(mp_parse_chunk_t) + parser.cur_chunk->alloc, - sizeof(mp_parse_chunk_t) + parser.cur_chunk->union_.used); + sizeof(mp_parse_chunk_t) + parser.cur_chunk->union_.used, + false); parser.cur_chunk->alloc = parser.cur_chunk->union_.used; parser.cur_chunk->union_.next = parser.tree.chunk; parser.tree.chunk = parser.cur_chunk; diff --git a/py/qstr.c b/py/qstr.c index 28df06ca3d..5aa1610648 100644 --- a/py/qstr.c +++ b/py/qstr.c @@ -199,7 +199,7 @@ qstr qstr_from_strn(const char *str, size_t len) { byte *new_p = m_renew_maybe(byte, MP_STATE_VM(qstr_last_chunk), MP_STATE_VM(qstr_last_alloc), MP_STATE_VM(qstr_last_alloc) + n_bytes, false); if (new_p == NULL) { // could not grow existing memory; shrink it to fit previous - (void)m_renew(byte, MP_STATE_VM(qstr_last_chunk), MP_STATE_VM(qstr_last_alloc), MP_STATE_VM(qstr_last_used)); + (void)m_renew_maybe(byte, MP_STATE_VM(qstr_last_chunk), MP_STATE_VM(qstr_last_alloc), MP_STATE_VM(qstr_last_used), false); MP_STATE_VM(qstr_last_chunk) = NULL; } else { // could grow existing memory