mirror of
https://github.com/netwide-assembler/nasm.git
synced 2024-11-21 03:14:19 +08:00
elf: support weak global and extern references
A global or extern definition can now contain the keyword "weak" (or "strong", although that is the default) to create a weak symbol or a weak external reference, respectively. Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
This commit is contained in:
H. Peter Anvin
parent
a73ccfebcc
commit
495fda6341
225
output/outelf.c
225
output/outelf.c
@ -727,12 +727,19 @@ static int32_t elf_section_names(char *name, int *bits)
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return s->index;
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}
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static inline bool sym_type_local(int type)
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{
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return ELF32_ST_BIND(type) == STB_LOCAL;
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}
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static void elf_deflabel(char *name, int32_t segment, int64_t offset,
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int is_global, char *special)
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{
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int pos = strslen;
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struct elf_symbol *sym;
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bool special_used = false;
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const char *spcword = nasm_skip_spaces(special);
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int bind, type; /* st_info components */
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const struct elf_section *sec = NULL;
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if (debug_level(2)) {
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nasm_debug(" elf_deflabel: %s, seg=%"PRIx32", off=%"PRIx64", is_global=%d, %s\n",
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@ -797,13 +804,13 @@ static void elf_deflabel(char *name, int32_t segment, int64_t offset,
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memset(&sym->symv, 0, sizeof(struct rbtree));
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sym->strpos = pos;
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sym->type = is_global ? SYM_GLOBAL : SYM_LOCAL;
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bind = is_global ? STB_GLOBAL : STB_LOCAL;
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type = STT_NOTYPE;
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sym->other = STV_DEFAULT;
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sym->size = 0;
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if (segment == NO_SEG)
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if (segment == NO_SEG) {
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sym->section = XSHN_ABS;
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else {
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const struct elf_section *s;
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} else {
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sym->section = XSHN_UNDEF;
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if (segment == def_seg) {
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/* we have to be sure at least text section is there */
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@ -811,9 +818,9 @@ static void elf_deflabel(char *name, int32_t segment, int64_t offset,
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if (segment != elf_section_names(".text", &tempint))
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nasm_panic("strange segment conditions in ELF driver");
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}
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s = raa_read_ptr(section_by_index, segment >> 1);
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if (s)
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sym->section = s->shndx;
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sec = raa_read_ptr(section_by_index, segment >> 1);
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if (sec)
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sym->section = sec->shndx;
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}
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if (is_global == 2) {
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@ -824,22 +831,133 @@ static void elf_deflabel(char *name, int32_t segment, int64_t offset,
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* We have a common variable. Check the special text to see
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* if it's a valid number and power of two; if so, store it
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* as the alignment for the common variable.
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*
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* XXX: this should allow an expression.
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*/
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if (special) {
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if (spcword) {
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bool err;
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sym->symv.key = readnum(special, &err);
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sym->symv.key = readnum(spcword, &err);
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if (err)
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nasm_nonfatal("alignment constraint `%s' is not a"
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" valid number", special);
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else if ((sym->symv.key | (sym->symv.key - 1)) != 2 * sym->symv.key - 1)
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else if (!is_power2(sym->symv.key))
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nasm_nonfatal("alignment constraint `%s' is not a"
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" power of two", special);
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spcword = nasm_skip_spaces(nasm_skip_word(spcword));
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}
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special_used = true;
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} else
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} else {
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sym->symv.key = (sym->section == XSHN_UNDEF ? 0 : offset);
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}
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if (sym->type == SYM_GLOBAL) {
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if (spcword && *spcword) {
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const char *wend;
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bool ok = true;
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while (ok) {
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size_t wlen;
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wend = nasm_skip_word(spcword);
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wlen = wend - spcword;
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switch (wlen) {
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case 4:
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if (!nasm_strnicmp(spcword, "data", wlen))
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type = STT_OBJECT;
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else if (!nasm_strnicmp(spcword, "weak", wlen))
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bind = STB_WEAK;
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else
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ok = false;
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break;
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case 6:
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if (!nasm_strnicmp(spcword, "notype", wlen))
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type = STT_NOTYPE;
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else if (!nasm_strnicmp(spcword, "object", wlen))
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type = STT_NOTYPE;
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else if (!nasm_strnicmp(spcword, "hidden", wlen))
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sym->other = STV_HIDDEN;
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else if (!nasm_strnicmp(spcword, "strong", wlen))
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bind = STB_GLOBAL;
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else
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ok = false;
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break;
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case 7:
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if (!nasm_strnicmp(spcword, "default", wlen))
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sym->other = STV_DEFAULT;
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else
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ok = false;
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break;
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case 8:
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if (!nasm_strnicmp(spcword, "function", wlen))
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type = STT_FUNC;
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else if (!nasm_stricmp(spcword, "internal"))
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sym->other = STV_INTERNAL;
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else
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ok = false;
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break;
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case 9:
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if (!nasm_strnicmp(spcword, "protected", wlen))
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sym->other = STV_PROTECTED;
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else
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ok = false;
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break;
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default:
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ok = false;
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break;
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}
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if (ok)
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spcword = nasm_skip_spaces(wend);
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}
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if (!is_global && bind != STB_LOCAL) {
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nasm_nonfatal("weak and strong only applies to global variables");
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bind = STB_LOCAL;
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}
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if (spcword && *spcword) {
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struct tokenval tokval;
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expr *e;
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int fwd = 0;
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char *saveme = stdscan_get();
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/*
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* We have a size expression; attempt to
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* evaluate it.
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*/
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stdscan_reset();
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stdscan_set((char *)spcword);
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tokval.t_type = TOKEN_INVALID;
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e = evaluate(stdscan, NULL, &tokval, &fwd, 0, NULL);
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if (fwd) {
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sym->nextfwd = fwds;
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fwds = sym;
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sym->name = nasm_strdup(name);
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} else if (e) {
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if (!is_simple(e))
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nasm_nonfatal("cannot use relocatable"
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" expression as symbol size");
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else
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sym->size = reloc_value(e);
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}
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stdscan_set(saveme);
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}
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}
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/*
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* If it is in a TLS segment, mark symbol accordingly.
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*/
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if (sec && (sec->flags & SHF_TLS))
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type = STT_TLS;
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/* Note: ELF32_ST_INFO() and ELF64_ST_INFO() are identical */
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sym->type = ELF32_ST_INFO(bind, type);
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if (sym_type_local(sym->type)) {
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nlocals++;
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} else {
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/*
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* If sym->section == SHN_ABS, then the first line of the
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* else section would cause a core dump, because its a reference
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@ -863,83 +981,10 @@ static void elf_deflabel(char *name, int32_t segment, int64_t offset,
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sects[sym->section-1]->gsyms =
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rb_insert(sects[sym->section-1]->gsyms, &sym->symv);
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if (special) {
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int n = strcspn(special, " \t");
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if (!nasm_strnicmp(special, "function", n))
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sym->type |= STT_FUNC;
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else if (!nasm_strnicmp(special, "data", n) ||
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!nasm_strnicmp(special, "object", n))
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sym->type |= STT_OBJECT;
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else if (!nasm_strnicmp(special, "notype", n))
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sym->type |= STT_NOTYPE;
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else
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nasm_nonfatal("unrecognised symbol type `%.*s'",
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n, special);
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special += n;
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special = nasm_skip_spaces(special);
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if (*special) {
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n = strcspn(special, " \t");
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if (!nasm_strnicmp(special, "default", n))
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sym->other = STV_DEFAULT;
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else if (!nasm_strnicmp(special, "internal", n))
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sym->other = STV_INTERNAL;
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else if (!nasm_strnicmp(special, "hidden", n))
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sym->other = STV_HIDDEN;
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else if (!nasm_strnicmp(special, "protected", n))
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sym->other = STV_PROTECTED;
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else
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n = 0;
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special += n;
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}
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if (*special) {
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struct tokenval tokval;
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expr *e;
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int fwd = 0;
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char *saveme = stdscan_get();
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while (special[n] && nasm_isspace(special[n]))
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n++;
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/*
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* We have a size expression; attempt to
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* evaluate it.
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*/
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stdscan_reset();
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stdscan_set(special + n);
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tokval.t_type = TOKEN_INVALID;
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e = evaluate(stdscan, NULL, &tokval, &fwd, 0, NULL);
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if (fwd) {
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sym->nextfwd = fwds;
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fwds = sym;
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sym->name = nasm_strdup(name);
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} else if (e) {
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if (!is_simple(e))
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nasm_nonfatal("cannot use relocatable"
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" expression as symbol size");
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else
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sym->size = reloc_value(e);
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}
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stdscan_set(saveme);
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}
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special_used = true;
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}
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/*
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* If TLS segment, mark symbol accordingly.
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*/
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if (sects[sym->section - 1]->flags & SHF_TLS) {
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sym->type &= 0xf0;
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sym->type |= STT_TLS;
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}
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}
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sym->globnum = nglobs;
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nglobs++;
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} else
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nlocals++;
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if (special && !special_used)
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nasm_nonfatal("no special symbol features supported here");
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}
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}
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static void elf_add_reloc(struct elf_section *sect, int32_t segment,
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@ -2133,7 +2178,7 @@ static size_t elf_build_symtab(void)
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*/
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saa_rewind(syms);
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while ((sym = saa_rstruct(syms))) {
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if (sym->type & SYM_GLOBAL)
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if (!sym_type_local(sym->type))
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continue;
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elf_sym(sym);
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@ -2146,7 +2191,7 @@ static size_t elf_build_symtab(void)
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*/
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saa_rewind(syms);
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while ((sym = saa_rstruct(syms))) {
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if (!(sym->type & SYM_GLOBAL))
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if (sym_type_local(sym->type))
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continue;
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elf_sym(sym);
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@ -41,10 +41,6 @@
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#include "rbtree.h"
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#include "saa.h"
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/* symbol binding */
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#define SYM_GLOBAL ELF32_ST_MKBIND(STB_GLOBAL)
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#define SYM_LOCAL ELF32_ST_MKBIND(STB_LOCAL)
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#define GLOBAL_TEMP_BASE 0x40000000 /* bigger than any sane symbol index */
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/* alignment of sections in file */
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@ -1,10 +1,27 @@
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global foo
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global foo:(foo_end - foo)
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global foo_hidden:function hidden
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global foo_protected:function protected
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global foo_internal:function internal
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global foo_weak:function weak
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global foo_hidden_weak:function hidden weak
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extern strong_ref, weak_ref:weak
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SECTION .text align=16
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foo:
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nop
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foo_hidden:
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nop
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foo_protected:
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nop
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foo_internal:
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nop
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foo_weak:
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ret
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foo_hidden_weak:
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mov eax,weak_ref
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mov eax,strong_ref
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foo_label:
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ret
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ret
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foo_end:
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