Re: [Tinycc-devel] Buggy commit "Rework expr_landor"

[grischka]

Christian Jullien wrote:
> Hi Michael,
>
> Your last commit breaks something in my bignum library used by OpenLisp.
>
> This library does a lot of logical and bit operations on integers.
>
> Only this last commit generates a core dump as tested on Linux x64 (tcc
> compiled by gcc 9.2.1) and Windows x64 (tcc compiled by boostrapped tcc).
>
> It is hard to currently investigate where it exactly happens.

Hi, well, here too, exactly what Christian wrote: strange failures,
hard to impossible to say more.  But I found another test that might
give a hint (attached).

About the precedence parser, great to see this, how it can really
work and all.

Still, hope you don't mind, I'd vote against it, for plain ordinary
nostalgic reasons, in the first place:

Basically those small functions making the top-down parser, still
almost unchanged from how Fabrice wrote them,  are a just wonderful
demonstration how simple C is, at its basics.  I figure everybody
seeing this wants to start working on her own compiler immediately.

We can't let that go away, can we?

About expr_landor,  I didn't feel quite happy with how it looks,
either.  Why for example

         if (c < 0)
             t = gvtst(i, t);
         else
             vpop();

and not just

         t = gvtst(i, t);

and let the "automatic code suppression" do it?  (Guess it was
const expressions or something.)

Obviously you tried to move these 'non-obviousnesses' to the
gvtest_set stuff.  I'm not sure that's a good idea.  At least
that part I was still able to understand.  Now, for example,
what means (t = gvtest()) == NULL?

         int t = gvtst(inv, 0);
         if (t) /* in case gvtst only needed to do a gsym */
           ...

Before that was because of nocode_wanted.  And that was the
reason why I did avoid to have any 'if' with it anywhere.

Anywho, there is less stack usage indeed, from compiling tcc.
On the other hand 6 or 7 kB (on i386) aren't that much either.

The patch to make those traces is attached too. Usage is
    $ tcc.exe -bt1000 -d9 tcc.c -o tcc1.exe
    $ tcc1.exe tcc.c -bench -d7 > tcc.log 2>&1

(1) with your patches:
      ../lib/bt-log.c:61: at test_stack: 6256
      ../tccpp.c:2772: parsing at 'next_nomacro1'
      ../tccgen.c:2223: by gen_opic
      ../tccgen.c:2683: by gen_op
      ...
      ../tcc.c:346: by main
      [60 levels]
      code: 220275 bytes, suppressed 327 bytes

(0) before:
      ../lib/bt-log.c:61: at test_stack: 7008
      ../tccpp.c:2772: parsing at 'next_nomacro1'
      ../tccgen.c:2214: by gen_opic
      ../tccgen.c:2674: by gen_op
      ...
      ../tcc.c:346: by main
      [136 levels]
      code: 220284 bytes, suppressed 327 bytes

--- grischka

> Christian.

>From 7b627bc4139ea609c5aeecbf8b85f96c3c1bfc3b Mon Sep 17 00:00:00 2001
From: grischka <grischka>
Date: Mon, 20 Jan 2020 08:46:39 +0100
Subject: stack test


diff --git a/i386-gen.c b/i386-gen.c
index 8016af94..cc601443 100644
--- a/i386-gen.c
+++ b/i386-gen.c
@@ -105,8 +105,14 @@ static void gen_bounds_epilog(void);
 ST_FUNC void g(int c)
 {
     int ind1;
-    if (nocode_wanted)
+
+    extern int cc, nc;
+    if (nocode_wanted) {
+        ++nc;
         return;
+    }
+    ++cc;
+
     ind1 = ind + 1;
     if (ind1 > cur_text_section->data_allocated)
         section_realloc(cur_text_section, ind1);
diff --git a/lib/bt-log.c b/lib/bt-log.c
index 73e0067f..87c4b7e2 100644
--- a/lib/bt-log.c
+++ b/lib/bt-log.c
@@ -34,3 +34,31 @@ DLL_EXPORT int tcc_backtrace(const char *fmt, ...)
     }
     return ret;
 }
+
+/* a stack depth test */
+char *main_stack;
+const char *ppfn;
+int *ppln;
+const char **ppfu;
+static unsigned xx;
+
+void test_stack()
+{
+    unsigned x;
+    const char *file, *func;
+    int line, level;
+
+    x = main_stack ? main_stack - (char*)&x : 0;
+    if (x <= xx)
+        return;
+    xx = x;
+    file = ppfn ? ppfn : 0;
+    line = ppln ? *ppln : 0;
+    func = ppfu ? *ppfu : 0;
+    if (func)
+        level = tcc_backtrace("%d\n%s:%d: parsing at '%s'", x, file, line, 
func);
+    else
+        level = tcc_backtrace("%d (not yet parsing)", x);
+
+    fprintf(stderr, "[%d levels]\n\n", level);
+}
diff --git a/libtcc.c b/libtcc.c
index fdbe2e7f..3bab0a8f 100644
--- a/libtcc.c
+++ b/libtcc.c
@@ -2084,8 +2084,15 @@ LIBTCCAPI void tcc_set_options(TCCState *s, const char 
*r)
     dynarray_reset(&argv, &argc);
 }

+int cc, nc;
+
 PUB_FUNC void tcc_print_stats(TCCState *s1, unsigned total_time)
 {
+    if (s1->g_debug == 7) {
+        fprintf(stderr, "code: %d bytes, suppressed %d bytes\n", cc, nc);
+        return;
+    }
+
     if (total_time < 1)
         total_time = 1;
     if (total_bytes < 1)
diff --git a/tcc.c b/tcc.c
index 34bfa004..009839e1 100644
--- a/tcc.c
+++ b/tcc.c
@@ -248,6 +248,9 @@ static unsigned getclock_ms(void)
 #endif
 }

+char* main_stack;
+int cc, nc;
+
 int main(int argc0, char **argv0)
 {
     TCCState *s, *s1;
@@ -257,6 +260,8 @@ int main(int argc0, char **argv0)
     int argc; char **argv;
     FILE *ppfp = stdout;

+    main_stack = (char*)&argc0;
+
 redo:
     argc = argc0, argv = argv0;
     s = s1 = tcc_new();
diff --git a/tccgen.c b/tccgen.c
index 047332b8..e4f047a9 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -7601,6 +7601,15 @@ static void decl_initializer_alloc(CType *type, 
AttributeDef *ad, int r,
     nocode_wanted = saved_nocode_wanted;
 }

+char *ppfn, *ppln, *ppfu;
+
+static void insert_func(const char *fn)
+{
+    int v = tok_alloc(fn, strlen(fn))->tok;
+    vpush_global_sym(&func_old_type, v);
+    gfunc_call(0);
+}
+
 /* parse a function defined by symbol 'sym' and generate its code in
    'cur_text_section' */
 static void gen_function(Sym *sym)
@@ -7633,7 +7642,15 @@ static void gen_function(Sym *sym)
     local_scope = 0;
     rsym = 0;
     clear_temp_local_var_list();
+
+    ppfn = (char*)&file->filename;
+    ppln = (char*)&file->line_num;
+    ppfu = (char*)&funcname;
+    if (tcc_state->g_debug == 9)
+        insert_func("test_stack");
     block(0);
+    ppfu = NULL;
+
     gsym(rsym);
     nocode_wanted = 0;
     /* reset local stack */
diff --git a/tccrun.c b/tccrun.c
index 4bf709d6..ae8001a0 100644
--- a/tccrun.c
+++ b/tccrun.c
@@ -564,7 +564,7 @@ static int _rt_error(void *fp, void *ip, const char *fmt, 
va_list ap)
     }

     rc->ip = rc->fp = 0;
-    return 0;
+    return level;
 }

 /* emit a run time error at position 'pc' */
diff --git a/x86_64-gen.c b/x86_64-gen.c
index 44c34ab0..f095fc26 100644
--- a/x86_64-gen.c
+++ b/x86_64-gen.c
@@ -150,8 +150,14 @@ static int func_ret_sub;
 ST_FUNC void g(int c)
 {
     int ind1;
-    if (nocode_wanted)
+
+    extern int cc, nc;
+    if (nocode_wanted) {
+        ++nc;
         return;
+    }
+    ++cc;
+
     ind1 = ind + 1;
     if (ind1 > cur_text_section->data_allocated)
         section_realloc(cur_text_section, ind1);


#include <stdio.h>
#include <string.h>

int main(int argc, char **argv)
{
    char buf[40];
    double a, b, n;
    int i = 0;

#define TEST_1(a,op,b) (a op b), ((a op b) && 1), !(a op b), (!(a op b) && 1)
#define TEST(op, ref) \
    sprintf(buf, "%d%d%d%d%d%d%d%d%d%d%d%d" \
        ,TEST_1(a, op, b) \
        ,TEST_1(b, op, a) \
        ,TEST_1(a, op, n) \
        ); \
    printf("%d: %-2s %s %s\n", ++i, #op, buf, strcmp(buf, ref) ? ref : "ok");

    a = 1, b = 1, n = 0, n = n/n;
    TEST(==, "110011000011");
    TEST(!=, "001100111100");
    a = -1;
    TEST(==, "001100110011");
    TEST(!=, "110011001100");
    TEST(<,  "110000110011");
    TEST(>,  "001111000011");
    return 0;
}