Rust Applications built on Centos7 cannot run on Centos6

[domibay-hugo]

I found this Thread about Rust sopporting RHEL6
#62516

But I actually found that Applications built on Centos7 cannot run on Centos6 because of high glibc requirements.
As documented in:
rust-lang/libc#1617

fn main() {
    println!("Hello, world!");
}

$ ./hello-world
./hello-world: /lib64/libc.so.6: version `GLIBC_2.14' not found (required by ./hello-world)

Reading that it would actually support EL6 makes me wonder why the highest available glibc Version is chosen on built time and not the actually required glibc Version.

[jonas-schievink]

I'm pretty sure this is expected behavior. The build system's libc is used to link the executable.

[domibay-hugo]

To achieve a real Backward Compatibility you would not require the newest Version but only this whose Functionality you really use.
As documented in the other Issue
rust-lang/libc#1617
other Compilers are completely backward compatible and do run on Centos6 when compiled on Centos7 because they do not require the newest available version.

$ ./hello-world_fpc.run
Hello, world!
$ ./hello-world_fpc.run -h
Usage: /path/to/hello-world_fpc.run -h

[domibay-hugo]

Going even further to build a backward and foreward compatible software you would not use the newest available Feature of the newest Version to be backward compatible and delete old obsolete Features to be foreward compatible
as documented in this issue:
#34668

[mati865]

You are probably talking about __cxa_thread_atexit_impl@@GLIBC_2.18 symbol

rust/src/libstd/sys/unix/fast_thread_local.rs

Lines 19 to 43 in d8bdb3f

	pub unsafe fn register_dtor(t: *mut u8, dtor: unsafe extern "C" fn(*mut u8)) {
	use crate::mem;
	use crate::sys_common::thread_local::register_dtor_fallback;
	extern "C" {
	#[linkage = "extern_weak"]
	static __dso_handle: *mut u8;
	#[linkage = "extern_weak"]
	static __cxa_thread_atexit_impl: *const libc::c_void;
	}
	if !__cxa_thread_atexit_impl.is_null() {
	type F = unsafe extern "C" fn(
	dtor: unsafe extern "C" fn(*mut u8),
	arg: *mut u8,
	dso_handle: *mut u8,
	) -> libc::c_int;
	mem::transmute::<*const libc::c_void, F>(__cxa_thread_atexit_impl)(
	dtor,
	t,
	&__dso_handle as *const _ as *mut _,
	);
	return;
	}
	register_dtor_fallback(t, dtor);
	}

It's used since Rust uses TLS during executable startup.

This is duplicate of #36826

[jonas-schievink]

Closing as duplicate, then.

[domibay-hugo]

I executed the Command documented at
#36826
on the Centos7 hello-world Application

$ objdump -T hello-world|grep -i glibc
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 getenv
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 dl_iterate_phdr
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.3.4 __snprintf_chk
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 free
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 abort
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 __errno_location
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_getattr_np
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 sigaction
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.3.4 __xpg_strerror_r
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 write
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 getpid
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.3.2 pthread_cond_wait
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 strlen
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_mutexattr_destroy
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.4   __stack_chk_fail
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 mmap
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_setspecific
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_mutex_destroy
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_mutexattr_init
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 strrchr
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 lseek
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 dladdr
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 memset
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_condattr_destroy
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 getcwd
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 close
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_attr_getstack
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 memchr
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 read
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 __libc_start_main
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 memcmp
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_attr_init
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.3   __tls_get_addr
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.3.2 pthread_cond_signal
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_rwlock_rdlock
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 strcmp
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 signal
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.14  memcpy
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.3.2 pthread_cond_init
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_getspecific
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_mutex_unlock
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_mutexattr_settype
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 malloc
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 __fxstat
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_rwlock_unlock
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.3.3 pthread_condattr_setclock
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 realloc
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 munmap
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_key_create
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_condattr_init
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 memmove
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_self
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 memrchr
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.3.2 pthread_cond_destroy
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 open
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 sysconf
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_attr_destroy
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_key_delete
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 bsearch
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 posix_memalign
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 sigaltstack
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_mutex_init
0000000000000000  w   DF *UND*	0000000000000000  GLIBC_2.2.5 __cxa_finalize
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.2.5 pthread_mutex_lock

The Function documented in
#36826
does not show up

Rather it shows that memcpy() would require GLIBC_2.14

$ objdump -T hello-world|grep -i glibc|grep -i "GLIBC_2.14"
0000000000000000      DF *UND*	0000000000000000  GLIBC_2.14  memcpy

so it is not duplicate

but it goes against the affirmation of "Rust being compatible with EL6"
because as documented in
rust-lang/libc#1617
Centos6 does only provide up to GLIBC_2.12

$ rpm -q --provides glibc|grep -i "GLIBC_"
libc.so.6(GLIBC_2.10)(64bit)  
libc.so.6(GLIBC_2.11)(64bit)  
libc.so.6(GLIBC_2.12)(64bit)  
libc.so.6(GLIBC_2.2.5)(64bit)  
libc.so.6(GLIBC_2.2.6)(64bit)  
libc.so.6(GLIBC_2.3)(64bit)  
libc.so.6(GLIBC_2.3.2)(64bit)  
libc.so.6(GLIBC_2.3.3)(64bit)  
libc.so.6(GLIBC_2.3.4)(64bit)  
libc.so.6(GLIBC_2.4)(64bit)  
libc.so.6(GLIBC_2.5)(64bit)  
libc.so.6(GLIBC_2.6)(64bit)  
libc.so.6(GLIBC_2.7)(64bit)  
libc.so.6(GLIBC_2.8)(64bit)  
libc.so.6(GLIBC_2.9)(64bit)  

but it also provides the memcpy function with GLIBC_2.2.5

$ objdump -T /lib64/libc.so.6|grep -i cpy|grep -i memcpy
0000000000091370  w   DF .text	0000000000000009  GLIBC_2.2.5 wmemcpy
00000000001010f0 g    DF .text	000000000000001b  GLIBC_2.4   __wmemcpy_chk
0000000000089720 g    DF .text	0000000000000465  GLIBC_2.2.5 memcpy
0000000000089710 g    DF .text	0000000000000009  GLIBC_2.3.4 __memcpy_chk

$ objdump -T /lib64/libc.so.6|grep -i cpy
00000000000ff460 g    DF .text	000000000000015d  GLIBC_2.3.4 __stpcpy_chk
0000000000091470  w   DF .text	00000000000000cb  GLIBC_2.2.5 wcpncpy
0000000000080c20 g   iD  .text	0000000000000029  GLIBC_2.2.5 strcpy
0000000000090e20  w   DF .text	0000000000000172  GLIBC_2.2.5 wcsncpy
0000000000101150 g    DF .text	0000000000000040  GLIBC_2.4   __wcpcpy_chk
000000000008d600 g    DF .text	000000000000009e  GLIBC_2.2.5 __strcpy_small
0000000000084d10  w  iD  .text	0000000000000029  GLIBC_2.2.5 stpncpy
0000000000091370  w   DF .text	0000000000000009  GLIBC_2.2.5 wmemcpy
00000000000845a0 g    DF .text	0000000000000009  GLIBC_2.3.4 __mempcpy_chk
0000000000082c90 g   iD  .text	0000000000000029  GLIBC_2.2.5 strncpy
0000000000101190 g    DF .text	0000000000000017  GLIBC_2.4   __wcsncpy_chk
0000000000084d10 g   iD  .text	0000000000000029  GLIBC_2.2.5 __stpncpy
00000000000896d0  w   DF .text	0000000000000033  GLIBC_2.2.5 memccpy
00000000000845b0  w   DF .text	0000000000000452  GLIBC_2.2.5 mempcpy
00000000001010f0 g    DF .text	000000000000001b  GLIBC_2.4   __wmemcpy_chk
00000000001010a0 g    DF .text	0000000000000043  GLIBC_2.4   __wcscpy_chk
0000000000101130 g    DF .text	000000000000001b  GLIBC_2.4   __wmempcpy_chk
0000000000091540  w   DF .text	0000000000000009  GLIBC_2.2.5 wmempcpy
0000000000089720 g    DF .text	0000000000000465  GLIBC_2.2.5 memcpy
00000000000ff8b0 g    DF .text	0000000000000186  GLIBC_2.3.4 __strncpy_chk
00000000000845b0 g    DF .text	0000000000000452  GLIBC_2.2.5 __mempcpy
0000000000090ba0 g    DF .text	0000000000000027  GLIBC_2.2.5 wcscpy
000000000008d530 g    DF .text	00000000000000c2  GLIBC_2.2.5 __mempcpy_small
000000000008d6a0 g    DF .text	000000000000009f  GLIBC_2.2.5 __stpcpy_small
0000000000089710 g    DF .text	0000000000000009  GLIBC_2.3.4 __memcpy_chk
00000000000ffa40 g    DF .text	00000000000000dc  GLIBC_2.4   __stpncpy_chk
0000000000084c00 g   iD  .text	0000000000000029  GLIBC_2.2.5 __stpcpy
00000000000ff620 g    DF .text	000000000000015d  GLIBC_2.3.4 __strcpy_chk
0000000000101350 g    DF .text	0000000000000017  GLIBC_2.4   __wcpncpy_chk
0000000000084c00  w  iD  .text	0000000000000029  GLIBC_2.2.5 stpcpy
0000000000091440  w   DF .text	0000000000000027  GLIBC_2.2.5 wcpcpy

It rather seems to have to do with the issue explained at:
https://stackoverflow.com/questions/35656696/explanation-of-memcpy-memmove-glibc-2-14-2-2-5

[jonas-schievink]

Interesting. It should still work when also building on CentOS 6 though, can you confirm this?

[domibay-hugo]

As mentioned in the Backward Compatibility thread
#62516 (comment)

Rust is not shipped for Centos6

For this reason I build the Application on Centos7 but I need to run them on Centos6, too.

[jonas-schievink]

#62516 (comment) implies that Rust should still work on older versions via rustup:

If our customers would like to use Rust on older RHEL, they can do so via rustup, and we'll support them in the same way we would for any other third-party software.