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lto-plugin.c
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lto-plugin.c
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/* LTO plugin for linkers like gold, GNU ld or mold.
Copyright (C) 2009-2024 Free Software Foundation, Inc.
Contributed by Rafael Avila de Espindola ([email protected]).
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; see the file COPYING3. If not see
<http:https://www.gnu.org/licenses/>. */
/* The plugin has only one external function: onload. A linker passes it an array of
function that the plugin uses to communicate back to the linker.
With the functions provided by the linker, the plugin can be notified when
the linker first analyzes a file and pass a symbol table back to the linker. The plugin
is also notified when all symbols have been read and it is time to generate
machine code for the necessary symbols.
More information at http:https://gcc.gnu.org/wiki/whopr/driver.
This plugin should be passed the lto-wrapper options and will forward them.
It also has options at his own:
-debug: Print the command line used to run lto-wrapper.
-nop: Instead of running lto-wrapper, pass the original to the plugin. This
only works if the input files are hybrid.
-linker-output-known: Do not determine linker output
-linker-output-auto-nolto-rel: Switch from rel to nolto-rel mode without
warning. This is used on systems like VxWorks (kernel) where the link is
always partial and repeated incremental linking is generally not used.
-sym-style={none,win32,underscore|uscore}
-pass-through */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#if HAVE_STDINT_H
#include <stdint.h>
#endif
#include <stdbool.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <inttypes.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#if HAVE_PTHREAD_LOCKING
#include <pthread.h>
#endif
#ifdef HAVE_SYS_WAIT_H
#include <sys/wait.h>
#endif
#ifndef WIFEXITED
#define WIFEXITED(S) (((S) & 0xff) == 0)
#endif
#ifndef WEXITSTATUS
#define WEXITSTATUS(S) (((S) & 0xff00) >> 8)
#endif
#include <libiberty.h>
#include <hashtab.h>
#include "../gcc/lto/common.h"
#include "simple-object.h"
#include "plugin-api.h"
/* We need to use I64 instead of ll width-specifier on native Windows.
The reason for this is that older MS-runtimes don't support the ll. */
#ifdef __MINGW32__
#define PRI_LL "I64"
#else
#define PRI_LL "ll"
#endif
/* Handle opening elf files on hosts, such as Windows, that may use
text file handling that will break binary access. */
#ifndef O_BINARY
# define O_BINARY 0
#endif
/* Segment name for LTO sections. This is only used for Mach-O.
FIXME: This needs to be kept in sync with darwin.c. */
#define LTO_SEGMENT_NAME "__GNU_LTO"
/* Return true if STR string starts with PREFIX. */
static inline bool
startswith (const char *str, const char *prefix)
{
return strncmp (str, prefix, strlen (prefix)) == 0;
}
/* The part of the symbol table the plugin has to keep track of. Note that we
must keep SYMS until all_symbols_read is called to give the linker time to
copy the symbol information.
The id must be 64bit to minimze collisions. */
struct sym_aux
{
uint32_t slot;
unsigned long long id;
unsigned next_conflict;
};
struct plugin_symtab
{
int nsyms;
int last_sym;
struct sym_aux *aux;
struct ld_plugin_symbol *syms;
unsigned long long id;
};
/* Encapsulates object file data during symbol scan. */
struct plugin_objfile
{
int found;
bool offload;
simple_object_read *objfile;
struct plugin_symtab *out;
const struct ld_plugin_input_file *file;
};
/* All that we have to remember about a file. */
struct plugin_file_info
{
char *name;
void *handle;
struct plugin_symtab symtab;
struct plugin_symtab conflicts;
bool skip_file;
};
/* List item with name of the file with offloading. */
struct plugin_offload_file
{
char *name;
struct plugin_offload_file *next;
};
/* Until ASM_OUTPUT_LABELREF can be hookized and decoupled from
stdio file streams, we do simple label translation here. */
enum symbol_style
{
ss_none, /* No underscore prefix. */
ss_win32, /* Underscore prefix any symbol not beginning with '@'. */
ss_uscore, /* Underscore prefix all symbols. */
};
#if HAVE_PTHREAD_LOCKING
/* Plug-in mutex. */
static pthread_mutex_t plugin_lock;
#define LOCK_SECTION pthread_mutex_lock (&plugin_lock)
#define UNLOCK_SECTION pthread_mutex_unlock (&plugin_lock)
#else
#define LOCK_SECTION
#define UNLOCK_SECTION
#endif
static char *arguments_file_name;
static ld_plugin_register_claim_file register_claim_file;
static ld_plugin_register_claim_file_v2 register_claim_file_v2;
static ld_plugin_register_all_symbols_read register_all_symbols_read;
static ld_plugin_get_symbols get_symbols, get_symbols_v2, get_symbols_v3;
static ld_plugin_register_cleanup register_cleanup;
static ld_plugin_add_input_file add_input_file;
static ld_plugin_add_input_library add_input_library;
static ld_plugin_message message;
static ld_plugin_add_symbols add_symbols, add_symbols_v2;
static ld_plugin_get_api_version get_api_version;
/* By default, use version LAPI_V0 if there is not negotiation. */
static enum linker_api_version api_version = LAPI_V0;
static struct plugin_file_info *claimed_files = NULL;
static unsigned int num_claimed_files = 0;
static unsigned int non_claimed_files = 0;
/* List of files with offloading. */
static struct plugin_offload_file *offload_files;
/* Last file in the list. */
static struct plugin_offload_file *offload_files_last;
/* Last non-archive file in the list. */
static struct plugin_offload_file *offload_files_last_obj;
/* Last LTO file in the list. */
static struct plugin_offload_file *offload_files_last_lto;
/* Total number of files with offloading. */
static unsigned num_offload_files;
static char **output_files = NULL;
static unsigned int num_output_files = 0;
static char **lto_wrapper_argv;
static int lto_wrapper_num_args;
static char **pass_through_items = NULL;
static unsigned int num_pass_through_items;
static char *ltrans_objects = NULL;
static bool debug;
static bool save_temps;
static bool verbose;
static char nop;
static char *resolution_file = NULL;
static enum ld_plugin_output_file_type linker_output;
static bool linker_output_set;
static bool linker_output_known;
static bool linker_output_auto_nolto_rel;
static const char *link_output_name = NULL;
/* This indicates link_output_name already contains the dot of the
suffix, so we can skip it in extensions. */
static bool skip_in_suffix = false;
/* The version of gold being used, or -1 if not gold. The number is
MAJOR * 100 + MINOR. */
static int gold_version = -1;
/* Not used by default, but can be overridden at runtime
by using -plugin-opt=-sym-style={none,win32,underscore|uscore}
(in fact, only first letter of style arg is checked.) */
static enum symbol_style sym_style = ss_none;
static void
check_1 (int gate, enum ld_plugin_level level, const char *text)
{
if (gate)
return;
if (message)
message (level, text);
else
{
/* If there is no nicer way to inform the user, fallback to stderr. */
fprintf (stderr, "%s\n", text);
if (level == LDPL_FATAL)
abort ();
}
}
/* This little wrapper allows check to be called with a non-integer
first argument, such as a pointer that must be non-NULL. We can't
use c99 bool type to coerce it into range, so we explicitly test. */
#define check(GATE, LEVEL, TEXT) check_1 (((GATE) != 0), (LEVEL), (TEXT))
/* Parse an entry of the IL symbol table. The data to be parsed is pointed
by P and the result is written in ENTRY. The slot number is stored in SLOT.
Returns the address of the next entry. */
static char *
parse_table_entry (char *p, struct ld_plugin_symbol *entry,
struct sym_aux *aux)
{
unsigned char t;
enum ld_plugin_symbol_kind translate_kind[] =
{
LDPK_DEF,
LDPK_WEAKDEF,
LDPK_UNDEF,
LDPK_WEAKUNDEF,
LDPK_COMMON
};
enum ld_plugin_symbol_visibility translate_visibility[] =
{
LDPV_DEFAULT,
LDPV_PROTECTED,
LDPV_INTERNAL,
LDPV_HIDDEN
};
switch (sym_style)
{
case ss_win32:
if (p[0] == '@')
{
/* cf. Duff's device. */
case ss_none:
entry->name = xstrdup (p);
break;
}
/* FALL-THROUGH. */
case ss_uscore:
entry->name = concat ("_", p, NULL);
break;
default:
check (0, LDPL_FATAL, "invalid symbol style requested");
break;
}
while (*p)
p++;
p++;
entry->version = NULL;
entry->comdat_key = p;
while (*p)
p++;
p++;
if (strlen (entry->comdat_key) == 0)
entry->comdat_key = NULL;
else
entry->comdat_key = xstrdup (entry->comdat_key);
entry->unused = entry->section_kind = entry->symbol_type = 0;
t = *p;
check (t <= 4, LDPL_FATAL, "invalid symbol kind found");
entry->def = translate_kind[t];
p++;
t = *p;
check (t <= 3, LDPL_FATAL, "invalid symbol visibility found");
entry->visibility = translate_visibility[t];
p++;
memcpy (&entry->size, p, sizeof (uint64_t));
p += 8;
memcpy (&aux->slot, p, sizeof (uint32_t));
p += 4;
entry->resolution = LDPR_UNKNOWN;
aux->next_conflict = -1;
return p;
}
/* Parse an entry of the IL symbol table. The data to be parsed is pointed
by P and the result is written in ENTRY. The slot number is stored in SLOT.
Returns the address of the next entry. */
static char *
parse_table_entry_extension (char *p, struct ld_plugin_symbol *entry)
{
unsigned char t;
enum ld_plugin_symbol_type symbol_types[] =
{
LDST_UNKNOWN,
LDST_FUNCTION,
LDST_VARIABLE,
};
t = *p;
check (t <= 2, LDPL_FATAL, "invalid symbol type found");
entry->symbol_type = symbol_types[t];
p++;
entry->section_kind = *p;
p++;
return p;
}
/* Translate the IL symbol table located between DATA and END. Append the
slots and symbols to OUT. */
static void
translate (char *data, char *end, struct plugin_symtab *out)
{
struct sym_aux *aux;
struct ld_plugin_symbol *syms = NULL;
int n, len;
/* This overestimates the output buffer sizes, but at least
the algorithm is O(1) now. */
len = (end - data)/8 + out->nsyms + 1;
syms = xrealloc (out->syms, len * sizeof (struct ld_plugin_symbol));
aux = xrealloc (out->aux, len * sizeof (struct sym_aux));
for (n = out->nsyms; data < end; n++)
{
aux[n].id = out->id;
data = parse_table_entry (data, &syms[n], &aux[n]);
}
assert(n < len);
out->nsyms = n;
out->syms = syms;
out->aux = aux;
}
static void
parse_symtab_extension (char *data, char *end, struct plugin_symtab *out)
{
unsigned long i;
unsigned char version;
if (data >= end)
/* FIXME: Issue an error ? */
return;
version = *data;
data++;
if (version != 1)
return;
/* Version 1 contains the following data per entry:
- symbol_type
- section_kind
. */
unsigned long nsyms = (end - data) / 2;
for (i = 0; i < nsyms; i++)
data = parse_table_entry_extension (data, out->syms + i + out->last_sym);
out->last_sym += nsyms;
}
/* Free all memory that is no longer needed after writing the symbol
resolution. */
static void
free_1 (struct plugin_file_info *files, unsigned num_files)
{
unsigned int i;
for (i = 0; i < num_files; i++)
{
struct plugin_file_info *info = &files[i];
struct plugin_symtab *symtab = &info->symtab;
unsigned int j;
for (j = 0; j < symtab->nsyms; j++)
{
struct ld_plugin_symbol *s = &symtab->syms[j];
free (s->name);
free (s->comdat_key);
}
free (symtab->syms);
symtab->syms = NULL;
}
}
/* Free all remaining memory. */
static void
free_2 (void)
{
unsigned int i;
for (i = 0; i < num_claimed_files; i++)
{
struct plugin_file_info *info = &claimed_files[i];
struct plugin_symtab *symtab = &info->symtab;
free (symtab->aux);
free (info->name);
}
for (i = 0; i < num_output_files; i++)
free (output_files[i]);
free (output_files);
free (claimed_files);
claimed_files = NULL;
num_claimed_files = 0;
while (offload_files)
{
struct plugin_offload_file *ofld = offload_files;
offload_files = offload_files->next;
free (ofld);
}
num_offload_files = 0;
free (arguments_file_name);
arguments_file_name = NULL;
}
/* Dump SYMTAB to resolution file F. */
static void
dump_symtab (FILE *f, struct plugin_symtab *symtab)
{
unsigned j;
for (j = 0; j < symtab->nsyms; j++)
{
uint32_t slot = symtab->aux[j].slot;
unsigned int resolution = symtab->syms[j].resolution;
assert (resolution != LDPR_UNKNOWN);
fprintf (f, "%u %" PRI_LL "x %s %s\n",
(unsigned int) slot, symtab->aux[j].id,
lto_resolution_str[resolution],
symtab->syms[j].name);
}
}
/* Finish the conflicts' resolution information after the linker resolved
the original symbols */
static void
finish_conflict_resolution (struct plugin_symtab *symtab,
struct plugin_symtab *conflicts)
{
int i, j;
if (conflicts->nsyms == 0)
return;
for (i = 0; i < symtab->nsyms; i++)
{
char resolution = LDPR_UNKNOWN;
if (symtab->aux[i].next_conflict == -1)
continue;
switch (symtab->syms[i].def)
{
case LDPK_DEF:
case LDPK_COMMON: /* ??? */
resolution = LDPR_RESOLVED_IR;
break;
case LDPK_WEAKDEF:
resolution = LDPR_PREEMPTED_IR;
break;
case LDPK_UNDEF:
case LDPK_WEAKUNDEF:
resolution = symtab->syms[i].resolution;
break;
default:
assert (0);
}
assert (resolution != LDPR_UNKNOWN);
for (j = symtab->aux[i].next_conflict;
j != -1;
j = conflicts->aux[j].next_conflict)
conflicts->syms[j].resolution = resolution;
}
}
/* Free symbol table SYMTAB. */
static void
free_symtab (struct plugin_symtab *symtab)
{
free (symtab->syms);
symtab->syms = NULL;
free (symtab->aux);
symtab->aux = NULL;
}
/* Writes the relocations to disk. */
static void
write_resolution (void)
{
unsigned int i, included_files = 0;
FILE *f;
check (resolution_file, LDPL_FATAL, "resolution file not specified");
f = fopen (resolution_file, "w");
check (f, LDPL_FATAL, "could not open file");
for (i = 0; i < num_claimed_files; i++)
{
struct plugin_file_info *info = &claimed_files[i];
struct plugin_symtab *symtab = &info->symtab;
struct ld_plugin_symbol *syms = symtab->syms;
/* Version 2 of API supports IRONLY_EXP resolution that is
accepted by GCC-4.7 and newer.
Version 3 can return LDPS_NO_SYMS that means the object
will not be used at all. */
if (get_symbols_v3)
{
enum ld_plugin_status status
= get_symbols_v3 (info->handle, symtab->nsyms, syms);
if (status == LDPS_NO_SYMS)
{
info->skip_file = true;
continue;
}
}
else if (get_symbols_v2)
get_symbols_v2 (info->handle, symtab->nsyms, syms);
else
get_symbols (info->handle, symtab->nsyms, syms);
++included_files;
finish_conflict_resolution (symtab, &info->conflicts);
}
fprintf (f, "%d\n", included_files);
for (i = 0; i < num_claimed_files; i++)
{
struct plugin_file_info *info = &claimed_files[i];
struct plugin_symtab *symtab = &info->symtab;
if (info->skip_file)
continue;
fprintf (f, "%s %d\n", info->name, symtab->nsyms + info->conflicts.nsyms);
dump_symtab (f, symtab);
if (info->conflicts.nsyms)
{
dump_symtab (f, &info->conflicts);
free_symtab (&info->conflicts);
}
}
fclose (f);
}
/* Pass files generated by the lto-wrapper to the linker. FD is lto-wrapper's
stdout. */
static void
add_output_files (FILE *f)
{
for (;;)
{
const unsigned piece = 32;
char *buf, *s = xmalloc (piece);
size_t len;
buf = s;
cont:
if (!fgets (buf, piece, f))
{
free (s);
break;
}
len = strlen (s);
if (s[len - 1] != '\n')
{
s = xrealloc (s, len + piece);
buf = s + len;
goto cont;
}
s[len - 1] = '\0';
num_output_files++;
output_files
= xrealloc (output_files, num_output_files * sizeof (char *));
output_files[num_output_files - 1] = s;
add_input_file (output_files[num_output_files - 1]);
}
}
/* Execute the lto-wrapper. ARGV[0] is the binary. The rest of ARGV is the
argument list. */
static void
exec_lto_wrapper (char *argv[])
{
int t, i;
int status;
char *at_args;
FILE *args;
FILE *wrapper_output;
char *new_argv[3];
struct pex_obj *pex;
const char *errmsg;
/* Write argv to a file to avoid a command line that is too long
Save the file locally on save-temps. */
const char *suffix = ".lto_wrapper_args";
if (skip_in_suffix)
suffix++;
if (save_temps && link_output_name)
arguments_file_name = concat (link_output_name, suffix, NULL);
else
arguments_file_name = make_temp_file (".lto_wrapper_args");
check (arguments_file_name, LDPL_FATAL,
"Failed to generate a temorary file name");
args = fopen (arguments_file_name, "w");
check (args, LDPL_FATAL, "could not open arguments file");
t = writeargv (&argv[1], args);
check (t == 0, LDPL_FATAL, "could not write arguments");
t = fclose (args);
check (t == 0, LDPL_FATAL, "could not close arguments file");
at_args = concat ("@", arguments_file_name, NULL);
check (at_args, LDPL_FATAL, "could not allocate");
for (i = 1; argv[i]; i++)
{
char *a = argv[i];
/* Check the input argument list for a verbose marker too. */
if (a[0] == '-' && a[1] == 'v' && a[2] == '\0')
{
verbose = true;
break;
}
}
if (verbose)
{
for (i = 0; argv[i]; i++)
fprintf (stderr, "%s ", argv[i]);
fprintf (stderr, "\n");
}
new_argv[0] = argv[0];
new_argv[1] = at_args;
new_argv[2] = NULL;
if (debug)
{
for (i = 0; new_argv[i]; i++)
fprintf (stderr, "%s ", new_argv[i]);
fprintf (stderr, "\n");
}
pex = pex_init (PEX_USE_PIPES, "lto-wrapper", NULL);
check (pex != NULL, LDPL_FATAL, "could not pex_init lto-wrapper");
errmsg = pex_run (pex, 0, new_argv[0], new_argv, NULL, NULL, &t);
check (errmsg == NULL, LDPL_FATAL, "could not run lto-wrapper");
check (t == 0, LDPL_FATAL, "could not run lto-wrapper");
wrapper_output = pex_read_output (pex, 0);
check (wrapper_output, LDPL_FATAL, "could not read lto-wrapper output");
add_output_files (wrapper_output);
t = pex_get_status (pex, 1, &status);
check (t == 1, LDPL_FATAL, "could not get lto-wrapper exit status");
check (WIFEXITED (status) && WEXITSTATUS (status) == 0, LDPL_FATAL,
"lto-wrapper failed");
pex_free (pex);
free (at_args);
}
/* Pass the original files back to the linker. */
static void
use_original_files (void)
{
unsigned i;
for (i = 0; i < num_claimed_files; i++)
{
struct plugin_file_info *info = &claimed_files[i];
add_input_file (info->name);
}
}
/* Called by the linker once all symbols have been read. */
static enum ld_plugin_status
all_symbols_read_handler (void)
{
const unsigned num_lto_args
= num_claimed_files + lto_wrapper_num_args + 2
+ !linker_output_known + !linker_output_auto_nolto_rel;
unsigned i;
char **lto_argv;
const char *linker_output_str = NULL;
const char **lto_arg_ptr;
if (num_claimed_files + num_offload_files == 0)
return LDPS_OK;
if (nop)
{
use_original_files ();
return LDPS_OK;
}
if (ltrans_objects)
{
FILE *objs = fopen (ltrans_objects, "r");
add_output_files (objs);
fclose (objs);
return LDPS_OK;
}
lto_argv = (char **) xcalloc (sizeof (char *), num_lto_args);
lto_arg_ptr = (const char **) lto_argv;
assert (lto_wrapper_argv);
write_resolution ();
free_1 (claimed_files, num_claimed_files);
for (i = 0; i < lto_wrapper_num_args; i++)
*lto_arg_ptr++ = lto_wrapper_argv[i];
if (!linker_output_known)
{
assert (linker_output_set);
switch (linker_output)
{
case LDPO_REL:
if (non_claimed_files)
{
if (!linker_output_auto_nolto_rel)
message (LDPL_WARNING, "incremental linking of LTO and non-LTO"
" objects; using -flinker-output=nolto-rel which will"
" bypass whole program optimization");
linker_output_str = "-flinker-output=nolto-rel";
}
else
linker_output_str = "-flinker-output=rel";
break;
case LDPO_DYN:
linker_output_str = "-flinker-output=dyn";
break;
case LDPO_PIE:
linker_output_str = "-flinker-output=pie";
break;
case LDPO_EXEC:
linker_output_str = "-flinker-output=exec";
break;
default:
message (LDPL_FATAL, "unsupported linker output %i", linker_output);
break;
}
*lto_arg_ptr++ = xstrdup (linker_output_str);
}
if (num_offload_files > 0)
{
FILE *f;
char *arg;
char *offload_objects_file_name;
struct plugin_offload_file *ofld;
const char *suffix = ".ofldlist";
if (save_temps && link_output_name)
{
suffix += skip_in_suffix;
offload_objects_file_name = concat (link_output_name, suffix, NULL);
}
else
offload_objects_file_name = make_temp_file (suffix);
check (offload_objects_file_name, LDPL_FATAL,
"Failed to generate a temporary file name");
f = fopen (offload_objects_file_name, "w");
check (f, LDPL_FATAL, "could not open file with offload objects");
fprintf (f, "%u\n", num_offload_files);
/* Skip the dummy item at the start of the list. */
ofld = offload_files->next;
while (ofld)
{
fprintf (f, "%s\n", ofld->name);
ofld = ofld->next;
}
fclose (f);
arg = concat ("-foffload-objects=", offload_objects_file_name, NULL);
check (arg, LDPL_FATAL, "could not allocate");
*lto_arg_ptr++ = arg;
}
for (i = 0; i < num_claimed_files; i++)
{
struct plugin_file_info *info = &claimed_files[i];
if (!info->skip_file)
*lto_arg_ptr++ = info->name;
}
*lto_arg_ptr++ = NULL;
exec_lto_wrapper (lto_argv);
free (lto_argv);
/* --pass-through is not needed when using gold 1.11 or later. */
if (pass_through_items && gold_version < 111)
{
unsigned int i;
for (i = 0; i < num_pass_through_items; i++)
{
if (startswith (pass_through_items[i], "-l"))
add_input_library (pass_through_items[i] + 2);
else
add_input_file (pass_through_items[i]);
free (pass_through_items[i]);
pass_through_items[i] = NULL;
}
free (pass_through_items);
pass_through_items = NULL;
}
return LDPS_OK;
}
/* Helper, as used in collect2. */
static int
file_exists (const char *name)
{
return access (name, R_OK) == 0;
}
/* Unlink FILE unless we have save-temps set.
Note that we're saving files if verbose output is set. */
static void
maybe_unlink (const char *file)
{
if (save_temps && file_exists (file))
{
if (verbose)
fprintf (stderr, "[Leaving %s]\n", file);
return;
}
unlink_if_ordinary (file);
}
/* Remove temporary files at the end of the link. */
static enum ld_plugin_status
cleanup_handler (void)
{
unsigned int i;
if (debug)
return LDPS_OK;
if (arguments_file_name)
maybe_unlink (arguments_file_name);
for (i = 0; i < num_output_files; i++)
maybe_unlink (output_files[i]);
free_2 ();
return LDPS_OK;
}
#define SWAP(type, a, b) \
do { type tmp_; tmp_ = (a); (a) = (b); (b) = tmp_; } while(0)
/* Compare two hash table entries */
static int eq_sym (const void *a, const void *b)
{
const struct ld_plugin_symbol *as = (const struct ld_plugin_symbol *)a;
const struct ld_plugin_symbol *bs = (const struct ld_plugin_symbol *)b;
return !strcmp (as->name, bs->name);
}
/* Hash a symbol */
static hashval_t hash_sym (const void *a)
{
const struct ld_plugin_symbol *as = (const struct ld_plugin_symbol *)a;
return htab_hash_string (as->name);
}
/* Determine how strong a symbol is */
static int symbol_strength (struct ld_plugin_symbol *s)
{
switch (s->def)
{
case LDPK_UNDEF:
case LDPK_WEAKUNDEF:
return 0;
case LDPK_WEAKDEF:
return 1;
default:
return 2;
}
}
/* In the ld -r case we can get dups in the LTO symbol tables, where
the same symbol can have different resolutions (e.g. undefined and defined).
We have to keep that in the LTO symbol tables, but the dups confuse
gold and then finally gcc by supplying incorrect resolutions.
Problem is that the main gold symbol table doesn't know about subids
and does not distingush the same symbols in different states.
So we drop duplicates from the linker visible symbol table
and keep them in a private table. Then later do own symbol
resolution for the duplicated based on the results for the