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macos: handle undefined symbols a bit

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at least data symbols coming from dylibs can be used now, as in the
below.  Note in the example that optind is defined in libc (really in
libsystem_c.dylib, reexported from libSystem.B.dylib):

static int loc;
extern int _optind;
int _start(void)
{
  _optind = 0;
  loc = 42 + _optind;
  return loc - 42;
}
This commit is contained in:
Michael Matz 2020-05-17 05:36:00 +02:00
parent fab8787b23
commit d82e64c163
1 changed files with 15 additions and 2 deletions
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17
tccmacho.c
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@ -220,6 +220,7 @@ struct macho {
};
#define SHT_LINKEDIT (SHT_LOOS + 42)
#define SHN_FROMDLL (SHN_LOOS + 2) /* Symbol is undefined, comes from a DLL */
#define LC_REQ_DYLD 0x80000000
#define LC_SYMTAB 0x2
@ -371,8 +372,18 @@ static int check_symbols(TCCState *s1, struct macho *mo)
mo->iundef = sym_index - 1;
if (ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
continue;
if (get_sym_attr(s1, elf_index, 0))
if (get_sym_attr(s1, elf_index, 0)) {
/* Mark the symbol as coming from a dylib so that
relocate_syms doesn't complain. Normally we would have
checked that any dylib in fact exports this one, and listed
those in s1->dynsymtab, which would cause us to enter this
symbol into s1->dynsym, which is checked by relocate_syms.
But for now we fake this and regard all undefined as
coming from a dylib, and we don't use the dynsymtab/dynsym
scheme. */
sym->st_shndx = SHN_FROMDLL;
continue;
}
tcc_error_noabort("undefined symbol '%s'", name);
ret = -1;
}
@ -399,6 +410,8 @@ static void convert_symbol(TCCState *s1, struct macho *mo, struct nlist_64 *pn)
ELFW(ST_TYPE)(sym->st_info), name);
}
if (sym->st_shndx == SHN_UNDEF)
tcc_error("should have been rewritten to SHN_FROMDLL");
else if (sym->st_shndx == SHN_FROMDLL)
n.n_type = 0 /* N_UNDF */, n.n_sect = 0;
else if (sym->st_shndx == SHN_ABS)
n.n_type = 2 /* N_ABS */, n.n_sect = 0;
@ -441,7 +454,7 @@ static int machosymcmp(const void *_a, const void *_b)
- (ELFW(ST_BIND)(sa->st_info) == STB_LOCAL);
if (r)
return r;
r = (sb->st_shndx == SHN_UNDEF) - (sa->st_shndx == SHN_UNDEF);
r = (sa->st_shndx == SHN_UNDEF) - (sb->st_shndx == SHN_UNDEF);
if (r)
return r;
if (ELFW(ST_BIND)(sa->st_info) != STB_LOCAL) {