cproc

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commit 385d7b257acf087e02114c619beee07f2b49cb41
parent 5b8a2d225ca3777c7b49421182bb5c1faf99ae64
Author: Michael Forney <mforney@mforney.org>
Date:   Wed,  3 Apr 2019 22:54:32 -0700

Parse bit-fields

Diffstat:
Mdecl.c | 79+++++++++++++++++++++++++++++++++++++++++++++++++++++++++----------------------
Mtype.h | 6++++++
Mutil.h | 3++-
3 files changed, 65 insertions(+), 23 deletions(-)

diff --git a/decl.c b/decl.c @@ -60,6 +60,7 @@ enum funcspec { struct structbuilder { struct type *type; struct member **last; + int bits; /* number of bits remaining in the last byte */ }; struct decl * @@ -206,6 +207,7 @@ tagspec(struct scope *s) case TYPEUNION: b.type = t; b.last = &t->structunion.members; + b.bits = 0; do structdecl(s, &b); while (tok.kind != TRBRACE); next(); @@ -640,29 +642,59 @@ paramdecl(struct scope *s, struct param *params) } static void -addmember(struct structbuilder *b, struct type *mt, char *name, int align) +addmember(struct structbuilder *b, struct type *mt, char *name, int align, uint64_t width) { struct type *t = b->type; struct member *m; - - m = xmalloc(sizeof(*m)); - m->type = mt; - m->name = name; - m->next = NULL; - *b->last = m; - b->last = &m->next; + size_t end; assert(mt->align > 0); - if (align < mt->align) + if (name || width == -1) { + m = xmalloc(sizeof(*m)); + m->type = mt; + m->name = name; + m->next = NULL; + *b->last = m; + b->last = &m->next; + } + if (width == -1) { + m->bits.before = 0; + m->bits.after = 0; + if (align < mt->align) + align = mt->align; + t->size = ALIGNUP(t->size, align); + if (t->kind == TYPESTRUCT) { + m->offset = t->size; + t->size += mt->size; + } else { + m->offset = 0; + if (t->size < mt->size) + t->size = mt->size; + } + } else { /* bit-field */ + if (!(typeprop(mt) & PROPINT)) + error(&tok.loc, "bit-field has invalid type"); + if (align) + error(&tok.loc, "alignment specified for bit-field"); + if (!width && name) + error(&tok.loc, "bit-field with zero width must not have declarator"); + if (width > mt->size * 8) + error(&tok.loc, "bit-field exceeds width of underlying type"); + /* calculate end of the storage-unit for this bit-field */ + end = ALIGNUP(t->size, mt->size); + if (!width || width > (end - t->size) * 8 + b->bits) { + /* no room, allocate a new storage-unit */ + t->size = end; + b->bits = 0; + } + if (width) { + m->offset = ALIGNDOWN(t->size - !!b->bits, mt->size); + m->bits.before = (t->size - m->offset) * 8 - b->bits; + m->bits.after = mt->size * 8 - width - m->bits.before; + t->size += (width - b->bits + 7) / 8; + b->bits = m->bits.after % 8; + } align = mt->align; - t->size = ALIGNUP(t->size, align); - if (t->kind == TYPESTRUCT) { - m->offset = t->size; - t->size += mt->size; - } else { - m->offset = 0; - if (t->size < mt->size) - t->size = mt->size; } if (t->align < align) t->align = align; @@ -673,6 +705,7 @@ structdecl(struct scope *s, struct structbuilder *b) { struct type *base, *mt; char *name; + uint64_t width; int align; base = declspecs(s, NULL, NULL, &align); @@ -682,16 +715,18 @@ structdecl(struct scope *s, struct structbuilder *b) if ((base->kind != TYPESTRUCT && base->kind != TYPEUNION) || base->structunion.tag) error(&tok.loc, "struct declaration must declare at least one member"); next(); - addmember(b, base, NULL, align); + addmember(b, base, NULL, align, -1); return; } for (;;) { - if (tok.kind != TCOLON) { + if (consume(TCOLON)) { + width = intconstexpr(s, false); + addmember(b, base, NULL, 0, width); + } else { mt = declarator(s, base, &name, false); - addmember(b, mt, name, align); + width = consume(TCOLON) ? intconstexpr(s, false) : -1; + addmember(b, mt, name, align, width); } - if (tok.kind == TCOLON) - error(&tok.loc, "bit-fields are not yet supported"); if (tok.kind == TSEMICOLON) break; expect(TCOMMA, "or ';' after declarator"); diff --git a/type.h b/type.h @@ -41,10 +41,16 @@ struct param { struct param *next; }; +struct bitfield { + short before; /* number of bits in the storage unit before the bit-field */ + short after; /* number of bits in the storage unit after the bit-field */ +}; + struct member { char *name; struct type *type; uint64_t offset; + struct bitfield bits; struct member *next; }; diff --git a/util.h b/util.h @@ -10,7 +10,8 @@ struct array { extern char *argv0; #define LEN(a) (sizeof(a) / sizeof((a)[0])) -#define ALIGNUP(x, n) (((x) + (n) - 1) & ~((n) - 1)) +#define ALIGNDOWN(x, n) ((x) & -(n)) +#define ALIGNUP(x, n) ALIGNDOWN((x) + (n) - 1, n) void warn(const char *, ...); _Noreturn void fatal(const char *fmt, ...);