https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87698
Bug ID: 87698
Summary: [lto] Shared library build with -ffat-lto-objects
generates extra global absolute symbol relocations
Product: gcc
Version: 8.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: lto
Assignee: unassigned at gcc dot gnu.org
Reporter: romain.geissler at amadeus dot com
CC: marxin at gcc dot gnu.org
Target Milestone: ---
Hi,
Is it expected that a shared library where each .o file has been built with
-flto -ffat-lto-objects has more symbol relocation (absolute symbol
relocations) than the very same shared library built with -flto
-ffat-lto-objects ?
With gcc 8.2.1 20181011 I have the following symbols defined in the case of fat
lto objects when building libssh2 (https://github.com/libssh2/libssh2):
/opt/1A/toolchain/x86_64-2.6.32-v4/bin/readelf -a
~combld/delivery/continuous/components.osp/osp/SSH2/18-0-0-0/lib/x86_64-2.6.32-v4/Debug/libssh2.so|grep
ABS
138: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_session_set_bloc
142: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_store_str
143: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_sha1_init
149: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_list_next
152: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_comp_methods
154: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_ntohu64
155: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_init_aes_ctr
159: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_dsa_sha1_verify
163: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_list_first
168: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_base64_encode
170: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_rsa_new_private_
172: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_pub_priv_keyfile
178: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_locate
179: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_kex_exchange
186: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_transport_read
187: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_extended
188: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_read
191: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_rsa_sha1_verify
194: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_packet_burn
198: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_ntohu32
200: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_userauth_publick
203: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_receive_
204: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_dsa_new_private_
205: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_pub_priv_keyfile
206: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_dsa_sha1_sign
209: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_free
215: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_list_init
217: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_write
223: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_htonu32
224: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_close
228: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_send
230: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_forward_
232: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_dsa_new_private
235: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_sha256_init
236: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_recv
245: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_md5_init
247: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_packet_requirev
250: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_process_
251: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_packet_require
260: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_list_add
264: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_wait_socket
265: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_packet_ask
267: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_cipher_init
271: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_rsa_sha1_sign
272: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_error_flags
273: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_rsa_new_private
275: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_dsa_new
282: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_error
285: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_cipher_crypt
290: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_store_u32
294: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_open
298: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_packet_add
299: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_init_if_needed
300: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_transport_send
301: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_calloc
302: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_packet_d
303: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_rsa_new
306: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS
_libssh2_channel_nextid
309: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_mac_methods
310: 0000000000000000 0 NOTYPE GLOBAL DEFAULT ABS _libssh2_list_remove
33: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
41: 0000000000000000 0 FILE LOCAL DEFAULT ABS
337: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
339: 0000000000000000 0 FILE LOCAL DEFAULT ABS
4605: 0000000000000000 0 FILE LOCAL DEFAULT ABS
The -fno-fat-lto-objects case gives:
/opt/1A/toolchain/x86_64-2.6.32-v4/bin/readelf -a .libs/libssh2.so|grep ABS
1:02AM 34: 0000000000000000 0 FILE LOCAL DEFAULT ABS
crtstuff.c
42: 0000000000000000 0 FILE LOCAL DEFAULT ABS
343: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
345: 0000000000000000 0 FILE LOCAL DEFAULT ABS
973: 0000000000000000 0 FILE LOCAL DEFAULT ABS
Also the final libssh2.so file size seems a bit different:
- fat objects: 656K
- slim objects: 596K
Is it expected that -ffat-lto-objects leaks data into shared library too ?
Cheers,
Romain
