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Fix access-after-free with statement expressions

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The return value of statement expressions might refer to local
symbols, so those can't be popped.  The old error message always
was just a band-aid, and since disabling it for pointer types it
wasn't effective anyway.  It also never considered that also the
vtop->sym member might have referred to such symbols (see the
testcase with the local static, that used to segfault).

For fixing this (can be seen better with valgrind and SYM_DEBUG)
simply leave local symbols of stmt exprs on the stack.
This commit is contained in:
Michael Matz
2016-08-15 05:09:31 +02:00
parent d0d25ec7df
commit be6d8ffc10
4 changed files with 76 additions and 29 deletions
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tcc.h
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@ -1099,7 +1099,7 @@ ST_INLN void sym_free(Sym *sym);
ST_FUNC Sym *sym_push2(Sym **ps, int v, int t, long c);
ST_FUNC Sym *sym_find2(Sym *s, int v);
ST_FUNC Sym *sym_push(int v, CType *type, int r, int c);
ST_FUNC void sym_pop(Sym **ptop, Sym *b);
ST_FUNC void sym_pop(Sym **ptop, Sym *b, int keep);
ST_INLN Sym *struct_find(int v);
ST_INLN Sym *sym_find(int v);
ST_FUNC Sym *global_identifier_push(int v, int t, int c);