From 43a11a7ed10a36eac6ab45a877fda9770de3ed40 Mon Sep 17 00:00:00 2001
From: Kirill Smelkov <kirr@navytux.spb.ru>
Date: Sat, 1 Dec 2012 01:00:23 +0400
Subject: [PATCH] Make tcc work after self-compiling with bounds-check enabled

For vstack Fabrice used the trick to initialize vtop to &vstack[-1], so
that on first push, vtop becomes &vstack[0] and a value is also stored
there - everything works.

Except that when tcc is compiled with bounds-checking enabled, vstack - 1
returns INVALID_POINTER and oops...

Let's workaround it with artificial 1 vstack slot which will not be
used, but only serve as an indicator that pointing to &vstack[-1] is ok.

Now, tcc, after being self-compiled with -b works:

    $ ./tcc -B. -o tccb  -DONE_SOURCE -DCONFIG_MULTIARCHDIR=\"i386-linux-gnu\" tcc.c  -ldl
    $ cd tests
    $ ../tcc -B.. -run tcctest.c >1
    $ ../tccb -B.. -run tcctest.c >2
    $ diff -u 1 2

and note, tcc's compilation speed is not affected:

    $ ./tcc -B. -bench -DONE_SOURCE -DCONFIG_MULTIARCHDIR=\"i386-linux-gnu\" -c tcc.c

    before: 8270 idents, 47221 lines, 1527730 bytes, 0.152 s, 309800 lines/s, 10.0 MB/s
    after:  8271 idents, 47221 lines, 1527733 bytes, 0.152 s, 310107 lines/s, 10.0 MB/s

But note, that `tcc -b -run tcc` is still broken - for example it crashes
on
    $ cat x.c
    double get100 () { return 100.0; }

    $ ./tcc -B. -b -DTCC_TARGET_I386 -DCONFIG_MULTIARCHDIR=\"i386-linux-gnu\"  -run   \
        -DONE_SOURCE ./tcc.c -B. -c x.c
    Runtime error: dereferencing invalid pointer
    ./tccpp.c:1953: at 0xa7beebdf parse_number() (included from ./libtcc.c, ./tcc.c)
    ./tccpp.c:3003: by 0xa7bf0708 next() (included from ./libtcc.c, ./tcc.c)
    ./tccgen.c:4465: by 0xa7bfe348 block() (included from ./libtcc.c, ./tcc.c)
    ./tccgen.c:4440: by 0xa7bfe212 block() (included from ./libtcc.c, ./tcc.c)
    ./tccgen.c:5529: by 0xa7c01929 gen_function() (included from ./libtcc.c, ./tcc.c)
    ./tccgen.c:5767: by 0xa7c02602 decl0() (included from ./libtcc.c, ./tcc.c)

that's because lib/bcheck.c runtime needs more fixes -- see next
patches.
---
 tcc.h    | 3 ++-
 tccgen.c | 2 +-
 tccpp.c  | 1 -
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tcc.h b/tcc.h
index 9e7c574..859c85f 100644
--- a/tcc.h
+++ b/tcc.h
@@ -1135,7 +1135,8 @@ ST_DATA Sym *local_label_stack;
 ST_DATA Sym *global_label_stack;
 ST_DATA Sym *define_stack;
 ST_DATA CType char_pointer_type, func_old_type, int_type, size_type;
-ST_DATA SValue vstack[VSTACK_SIZE], *vtop;
+ST_DATA SValue __vstack[1+/*to make bcheck happy*/ VSTACK_SIZE], *vtop;
+#define vstack  (__vstack + 1)
 ST_DATA int rsym, anon_sym, ind, loc;
 
 ST_DATA int const_wanted; /* true if constant wanted */
diff --git a/tccgen.c b/tccgen.c
index f79da36..b9142d2 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -55,7 +55,7 @@ ST_DATA Sym *define_stack;
 ST_DATA Sym *global_label_stack;
 ST_DATA Sym *local_label_stack;
 
-ST_DATA SValue vstack[VSTACK_SIZE], *vtop;
+ST_DATA SValue __vstack[1+VSTACK_SIZE], *vtop;
 
 ST_DATA int const_wanted; /* true if constant wanted */
 ST_DATA int nocode_wanted; /* true if no code generation wanted for an expression */
diff --git a/tccpp.c b/tccpp.c
index aff5a53..b80c986 100644
--- a/tccpp.c
+++ b/tccpp.c
@@ -3041,7 +3041,6 @@ ST_FUNC void preprocess_init(TCCState *s1)
     s1->ifdef_stack_ptr = s1->ifdef_stack;
     file->ifdef_stack_ptr = s1->ifdef_stack_ptr;
 
-    /* XXX: not ANSI compliant: bound checking says error */
     vtop = vstack - 1;
     s1->pack_stack[0] = 0;
     s1->pack_stack_ptr = s1->pack_stack;