From 5c6356ff8e8ad57c8d5ad8220d665dfba02290cf Mon Sep 17 00:00:00 2001
From: herman ten brugge <hermantenbrugge@home.nl>
Date: Fri, 18 Sep 2020 19:20:57 +0200
Subject: [PATCH] default-initialization of bitfields

The code:

struct bf_SS {unsigned int bit:1,bits31:31; };
void func(void) {
  struct bf_SS bf_finit = { .bit = 1 };
}

will not init bits31 to 0.

tccgen.c:
- check_bf: New function to check if bitfield is present in struct/union
- decl_initializer: Call check_bf and set value to 0 is bitfield found

tests/tcctest.c:
- Add struct bitfield test code
---
 tccgen.c        | 25 +++++++++++++++++++++++++
 tests/tcctest.c | 31 +++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)

diff --git a/tccgen.c b/tccgen.c
index 0be3a52a..c46adfd1 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -7651,6 +7651,23 @@ static void init_putv(CType *type, Section *sec, unsigned long c)
     }
 }
 
+/* Check for bitfield in struct/union recursive */
+static int check_bf(Sym *f)
+{
+   while (f->next) {
+       f = f->next;
+       if ((f->type.t & VT_BITFIELD) ||
+           ((f->type.t & VT_BTYPE) == VT_STRUCT && check_bf(f->type.ref)))
+           return 1;
+       if (f->type.t & VT_ARRAY) {
+           Sym *r = f->type.ref;
+           if (((r->type.t & VT_BTYPE) == VT_STRUCT && check_bf(r->type.ref)))
+               return 1;
+       }
+    }
+    return 0;
+}
+
 /* 't' contains the type and storage info. 'c' is the offset of the
    object in section 'sec'. If 'sec' is NULL, it means stack based
    allocation. 'flags & DIF_FIRST' is true if array '{' must be read (multi
@@ -7688,6 +7705,11 @@ static void decl_initializer(CType *type, Section *sec, unsigned long c,
         t1 = pointed_type(type);
         size1 = type_size(t1, &align1);
 
+        if (!(flags & DIF_SIZE_ONLY) &&
+            (s->type.t & VT_BTYPE) == VT_STRUCT && check_bf (s->type.ref))
+            /* If there is a bitfield in array clear it */
+            init_putz(sec, c, size1 * n);
+
         no_oblock = 1;
         if (((flags & DIF_FIRST) && tok != TOK_LSTR && tok != TOK_STR) ||
             tok == '{') {
@@ -7817,6 +7839,9 @@ static void decl_initializer(CType *type, Section *sec, unsigned long c,
         s = type->ref;
         f = s->next;
         n = s->c;
+        if (!(flags & DIF_SIZE_ONLY) && check_bf (s))
+            /* If there is a bitfield in struct/union clear it */
+            init_putz(sec, c, n);
 	goto do_init_list;
     } else if (tok == '{') {
         if (flags & DIF_HAVE_ELEM)
diff --git a/tests/tcctest.c b/tests/tcctest.c
index 4696779d..f72b6519 100644
--- a/tests/tcctest.c
+++ b/tests/tcctest.c
@@ -1737,6 +1737,16 @@ int sinit23[2] = { "astring" ? sizeof("astring") : -1,
 
 int sinit24 = 2 || 1 / 0; /* exception in constant but unevaluated context */
 
+/* bitfield init */
+struct bf_SS {unsigned int bit:1,bits31:31; };
+struct bf_SS bf_init = { .bit = 1 };
+struct bfn_SS {int a,b; struct bf_SS c; int d,e; };
+struct bfn_SS bfn_init = { .c.bit = 1 };
+struct bfa_SS {int a,b; struct bf_SS c[3]; int d,e; };
+struct bfa_SS bfa_init = { .c[1].bit = 1 };
+struct bf_SS bfaa_init[3] = { [1].bit = 1 };
+struct bf_SS bfaa_vinit[] = { [2].bit = 1 };
+
 extern int external_inited = 42;
 
 void init_test(void)
@@ -1756,6 +1766,11 @@ void init_test(void)
     int zero = 0;
     /* Addresses on non-weak symbols are non-zero, but not the access itself */
     int linit18[2] = {&zero ? 1 : -1, zero ? -1 : 1 };
+    struct bf_SS bf_finit = { .bit = 1 };
+    struct bfn_SS bfn_finit = { .c.bit = 1 };
+    struct bfa_SS bfa_finit = { .c[1].bit = 1 };
+    struct bf_SS bfaa_finit[3] = { [1].bit = 1 };
+    struct bf_SS bfaa_fvinit[] = { [2].bit = 1 };
     
     printf("sinit1=%d\n", sinit1);
     printf("sinit2=%d\n", sinit2);
@@ -1851,6 +1866,22 @@ void init_test(void)
     printf("sinit23= %d %d\n", sinit23[0], sinit23[1]);
     printf("sinit24=%d\n", sinit24);
     printf("linit18= %d %d\n", linit18[0], linit18[1]);
+    printf ("bf1: %u %u\n", bf_init.bit, bf_init.bits31);
+    printf ("bf2: %u %u\n", bf_finit.bit, bf_finit.bits31);
+    printf ("bf3: %u %u\n", bfn_init.c.bit, bfn_init.c.bits31);
+    printf ("bf4: %u %u\n", bfn_finit.c.bit, bfn_finit.c.bits31);
+    for (i = 0; i < 3; i++)
+        printf ("bf5[%d]: %u %u\n", i, bfa_init.c[i].bit, bfa_init.c[i].bits31);
+    for (i = 0; i < 3; i++)
+        printf ("bf6[%d]: %u %u\n", i, bfa_finit.c[i].bit, bfa_finit.c[i].bits31);
+    for (i = 0; i < 3; i++)
+        printf ("bf7[%d]: %u %u\n", i, bfaa_init[i].bit, bfaa_init[i].bits31);
+    for (i = 0; i < 3; i++)
+        printf ("bf8[%d]: %u %u\n", i, bfaa_finit[i].bit, bfaa_finit[i].bits31);
+    for (i = 0; i < 3; i++)
+        printf ("bf9[%d]: %u %u\n", i, bfaa_vinit[i].bit, bfaa_vinit[i].bits31);
+    for (i = 0; i < 3; i++)
+        printf ("bf10[%d]: %u %u\n", i, bfaa_fvinit[i].bit, bfaa_fvinit[i].bits31);
 }
 
 void switch_uc(unsigned char uc)
-- 
2.11.4.GIT