erlang is built differently in 4.0.2 and 4.0.4 docker images

[rstrlcpy]

Community Docker image

Steps to reproduce the behavior in question

Hello.
I noticed Erlang in 4.0.4 docker image was build with USE_SELECT while 4.0.[2,3] was build build without the flag. Could someone explain why?
Because of that 4.0.4 uses select as fallback-pollset while 4.0.[2,3] use poll and that causes warnings on UI because FDs limit is 1024 for the select.

4.0.4

$ docker run --rm -it rabbitmq:4.0.4-management-alpine /bin/bash
# echo "erlang:system_info(compile_info)." | erl | egrep -o "define USE_SELECT 1"
# define USE_SELECT 1
# 1

# echo "erlang:system_info(check_io)." | erl
Erlang/OTP 27 [erts-15.2] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit:ns]

Eshell V15.2 (press Ctrl+G to abort, type help(). for help)
1> [[{name,erts_poll},
  {primary,select},    <<<<<<<<<<<
  {kernel_poll,false},
  {memory_size,13448},
  {total_poll_set_size,1},
  {lazy_updates,true},
  {pending_updates,0},
  {batch_updates,false},
  {concurrent_updates,false},
  {fallback,true},
  {max_fds,1024},    <<<<<<<<<<<<
  {active_fds,0},
  {poll_threads,0}],

4.0.2

$ docker run --rm -it rabbitmq:4.0.2-management-alpine /bin/bash
# echo "erlang:system_info(compile_info)." | erl | egrep -o "define USE_SELECT 1"
# 0

# echo "erlang:system_info(check_io)." | erl
Erlang/OTP 26 [erts-14.2.5.4] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit]

Eshell V14.2.5.4 (press Ctrl+G to abort, type help(). for help)
1> [[{name,erts_poll},
  {primary,poll}, <<<<<<<<<<<<<<
  {kernel_poll,false},
  {memory_size,25240},
  {total_poll_set_size,1},
  {lazy_updates,true},
  {pending_updates,0},
  {batch_updates,false},
  {concurrent_updates,false},
  {fallback,true},
  {max_fds,1048576},   <<<<<<<<<<<<<<<<
  {active_fds,0},
  {poll_threads,0}],

4.0.3

$ docker run --rm -it rabbitmq:4.0.2-management-alpine /bin/bash
# echo "erlang:system_info(compile_info)." | erl | egrep -o "define USE_SELECT 1"
# 0

echo "erlang:system_info(check_io)." | erl
Erlang/OTP 26 [erts-14.2.5.4] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit]

Eshell V14.2.5.4 (press Ctrl+G to abort, type help(). for help)
1> [[{name,erts_poll},
  {primary,poll},     <<<<<<<<<<<<<<<<
  {kernel_poll,false},
  {memory_size,25240},
  {total_poll_set_size,1},
  {lazy_updates,true},
  {pending_updates,0},
  {batch_updates,false},
  {concurrent_updates,false},
  {fallback,true},
  {max_fds,1048576},    <<<<<<<<<<<<<<<<
  {active_fds,0},
  {poll_threads,0}],

[lukebakken]

I noticed Erlang in 4.0.4 docker image was build with USE_SELECT while 4.0.[2,3] was build build without the flag. Could someone explain why?

This probably has to do with the upgrade of the underlying Alpine image. Here is how the Erlang build sets USE_SELECT:

https://github.com/erlang/otp/blob/master/erts/configure.ac#L3139-L3191

I'm running a build of the alpine docker image to see what is logged.

[lukebakken]

#10 16.02 checking for working poll()... no; non-existing, broken, or based on select()

Hmm 🤔

[lukebakken]

This test code works just fine on a bare Alpine 3.21 VM with the same dev tools installed as the Dockerfile:

Code:

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
int main()
{
#ifdef _POLL_EMUL_H_
  printf("POLL_EMUL_H is defined!\n");
  exit(1); /* Implemented using select() -- fail */
#else
  struct pollfd fds[1];
  int fd;
  fd = open("/dev/null", 1);
  fds[0].fd = fd;
  fds[0].events = POLLIN;
  fds[0].revents = 0;
  if (poll(fds, 1, 0) < 0 || (fds[0].revents & POLLNVAL) != 0) {
    printf("poll failed!\n");
    exit(1);  /* Does not work for devices -- fail */
  }
  exit(0);
#endif
}

Output:

b0c882ad5161:/# ./a.out; echo $?
0                                 

[lukebakken]

OK, it looks like the test that is run by the Erlang configure script is missing important header files that need to be there on Alpine. I saw these same errors in the test code above until I added several header file include statements. I suspect that gcc got a lot less forgiving by default. I'll compare with the output on Ubuntu.

conftest.c and output

configure:25844: checking for working poll()
configure:25889: gcc -o conftest -fno-strict-aliasing -fno-common -g -O2 -Wl,-rpath=/opt/openssl/lib -I/usr/local/src/otp-27.2/erts/x86_64-pc-linux-musl   -D_GNU_SOURCE  conftest.c -lutil -ldl -lm   >&5
conftest.c:258:1: error: return type defaults to 'int' [-Wimplicit-int]
  258 | main()
      | ^~~~
conftest.c: In function 'main':
conftest.c:265:8: error: implicit declaration of function 'open' [-Wimplicit-function-declaration]
  265 |   fd = open("/dev/null", 1);
      |        ^~~~
conftest.c:270:5: error: implicit declaration of function 'exit' [-Wimplicit-function-declaration]
  270 |     exit(1);  /* Does not work for devices -- fail */
      |     ^~~~
conftest.c:258:1: note: include '<stdlib.h>' or provide a declaration of 'exit'
  257 | #include <poll.h>
  +++ |+#include <stdlib.h>
  258 | main()
conftest.c:270:5: warning: incompatible implicit declaration of built-in function 'exit' [-Wbuiltin-declaration-mismatch]
  270 |     exit(1);  /* Does not work for devices -- fail */
      |     ^~~~
conftest.c:270:5: note: include '<stdlib.h>' or provide a declaration of 'exit'
conftest.c:272:3: warning: incompatible implicit declaration of built-in function 'exit' [-Wbuiltin-declaration-mismatch]
  272 |   exit(0);
      |   ^~~~
conftest.c:272:3: note: include '<stdlib.h>' or provide a declaration of 'exit'
configure:25889: $? = 1
configure: program exited with status 1
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME ""
| #define PACKAGE_TARNAME ""
| #define PACKAGE_VERSION ""
| #define PACKAGE_STRING ""
| #define PACKAGE_BUGREPORT ""
| #define PACKAGE_URL ""
| #define ASSUMED_CACHE_LINE_SIZE 64
| #define ERTS_ENABLE_MSACC 2
| #define ERTS_NO_RETPOLINE 
| #define HAVE_STDIO_H 1
| #define HAVE_STDLIB_H 1
| #define HAVE_STRING_H 1
| #define HAVE_INTTYPES_H 1
| #define HAVE_STDINT_H 1
| #define HAVE_STRINGS_H 1
| #define HAVE_SYS_STAT_H 1
| #define HAVE_SYS_TYPES_H 1
| #define HAVE_UNISTD_H 1
| #define HAVE_SYS_TIME_H 1
| #define STDC_HEADERS 1
| #define SIZEOF_TIME_T 8
| #define SIZEOF_VOID_P 8
| #define HAVE_LIBM 1
| #define HAVE_LIBDL 1
| #define HAVE_LIBUTIL 1
| #define ETHR_TRUST_GCC_ATOMIC_BUILTINS_MEMORY_BARRIERS 0
| #define SIZEOF_VOID_P 8
| #define HAVE_PTHREAD_H 1
| #define HAVE_CLOCK_GETRES 1
| #define ETHR_HAVE_CLOCK_GETTIME_MONOTONIC 1
| #define ETHR_MONOTONIC_CLOCK_ID CLOCK_MONOTONIC
| #define ETHR_PTHREADS 1
| #define ETHR_HAVE_PTHREAD_H 1
| #define ETHR_HAVE_SCHED_H 1
| #define ETHR_HAVE_SYS_TIME_H 1
| #define ETHR_HAVE_USABLE_PTHREAD_STACK_MIN 1
| #define ETHR_HAVE_PTHREAD_SPIN_LOCK 1
| #define ETHR_HAVE_SCHED_YIELD 1
| #define ETHR_SCHED_YIELD_RET_INT 1
| #define ETHR_HAVE_PTHREAD_ATTR_SETGUARDSIZE 1
| #define ETHR_HAVE_PTHREAD_COND_TIMEDWAIT_MONOTONIC 1
| #define ETHR_HAVE_LINUX_FUTEX 1
| #define ETHR_HAVE_PTHREAD_SETNAME_NP_2 1
| #define ETHR_HAVE_PTHREAD_GETNAME_NP_3 1
| #define SIZEOF_SHORT 2
| #define SIZEOF_INT 4
| #define SIZEOF_LONG 8
| #define SIZEOF_LONG_LONG 8
| #define SIZEOF___INT128_T 16
| #define ETHR_HAVE___sync_synchronize ~0
| #define ETHR_HAVE___sync_add_and_fetch 12
| #define ETHR_HAVE___sync_fetch_and_and 12
| #define ETHR_HAVE___sync_fetch_and_or 12
| #define ETHR_HAVE___sync_val_compare_and_swap 12
| #define ETHR_HAVE___atomic_store_n 12
| #define ETHR_HAVE___atomic_load_n 12
| #define ETHR_HAVE___atomic_add_fetch 12
| #define ETHR_HAVE___atomic_fetch_and 12
| #define ETHR_HAVE___atomic_fetch_or 12
| #define ETHR_HAVE___atomic_compare_exchange_n 12
| #define ETHR_HAVE_GCC_ASM_ARM_DMB_INSTRUCTION 0
| #define ETHR_HAVE_GCC_ASM_ARM_DMB_ST_INSTRUCTION 0
| #define ETHR_HAVE_GCC_ASM_ARM_DMB_LD_INSTRUCTION 0
| #define ETHR_HAVE_GCC_ASM_ARM_ISB_SY_INSTRUCTION 0
| #define ETHR_HAVE_GCC_ASM_ARM_DC_CVAU_INSTRUCTION 0
| #define ETHR_HAVE_GCC_ASM_ARM_IC_IVAU_INSTRUCTION 0
| #define ETHR_HAVE_GCC___ATOMIC_BUILTINS 1
| #define SIZEOF_VOID_P 8
| #define ETHR_SIZEOF_PTR 8
| #define SIZEOF_INT 4
| #define ETHR_SIZEOF_INT 4
| #define SIZEOF_LONG 8
| #define ETHR_SIZEOF_LONG 8
| #define SIZEOF_LONG_LONG 8
| #define ETHR_SIZEOF_LONG_LONG 8
| #define SIZEOF___INT64 0
| #define ETHR_SIZEOF___INT64 0
| #define SIZEOF___INT128_T 16
| #define ETHR_SIZEOF___INT128_T 16
| #define ETHR_GCC_HAVE_DW_CMPXCHG_ASM_SUPPORT 1
| #define ETHR_HAVE_ETHREAD_DEFINES 1
| #define ETHR_SMP_REQUIRE_NATIVE_IMPLS 1
| #define HAVE_POSIX_FADVISE 1
| #define HAVE_LINUX_FALLOC_H 1
| #define HAVE_FALLOCATE 1
| #define HAVE_POSIX_FALLOCATE /**/
| #define ERTS_NEED_DLOPEN_BEFORE_DLERROR 1
| #define HAVE_TERMCAP_H 1
| #define HAVE_CURSES_H 1
| #define HAVE_TERM_H 1
| #define HAVE_TERMCAP 1
| #define HAVE_WCWIDTH 1
| #define HAVE_ZLIB_INFLATEGETDICTIONARY 1
| #define ESOCK_ENABLE 1
| #define HAVE_LOCALTIME_R 1
| #define HAVE_STRFTIME 1
| #define HAVE_GETPROTOENT 1
| #define HAVE_SETPROTOENT 1
| #define HAVE_ENDPROTOENT 1
| #define ESOCK_USE_EXTENDED_ERROR_INFO 1
| #define ESOCK_COUNTER_SIZE 64
| #define HAVE_IF_NAMETOINDEX 1
| #define HAVE_IF_INDEXTONAME 1
| #define HAVE_IF_NAMEINDEX 1
| #define HAVE_IF_FREENAMEINDEX 1
| #define HAVE_GETHOSTNAME 1
| #define ESOCK_USE_SOCKET_REGISTRY 1
| #define HAVE_STRUCT_IFREQ_IFR_MAP 1
| #define ESOCK_USE_IFMAP /**/
| #define HAVE_STRUCT_IFREQ_IFR_HWADDR 1
| #define ESOCK_USE_HWADDR /**/
| #define HAVE_STRUCT_IFREQ_IFR_IFINDEX 1
| #define ESOCK_USE_IFINDEX /**/
| #define HAVE_WORKING_POSIX_OPENPT 1
| #define NETDB_H_NEEDS_IN_H 1
| #define HAVE_SOCKLEN_T 1
| #define H_ERRNO_DECLARED 1
| #define HAVE_DIRENT_H 1
| #define HAVE_SYS_WAIT_H 1
| #define HAVE_FCNTL_H 1
| #define HAVE_LIMITS_H 1
| #define HAVE_UNISTD_H 1
| #define HAVE_SYSLOG_H 1
| #define HAVE_DLFCN_H 1
| #define HAVE_SYS_TYPES_H 1
| #define HAVE_SYS_STROPTS_H 1
| #define HAVE_SYS_IOCTL_H 1
| #define HAVE_SYS_TIME_H 1
| #define HAVE_SYS_UIO_H 1
| #define HAVE_SYS_MMAN_H 1
| #define HAVE_SYS_SOCKET_H 1
| #define HAVE_MALLOC_H 1
| #define HAVE_ARPA_NAMESER_H 1
| #define HAVE_PTY_H 1
| #define HAVE_UTMP_H 1
| #define HAVE_LANGINFO_H 1
| #define HAVE_POLL_H 1
| #define HAVE_ELF_H 1
| #define HAVE_STRUCT_IFREQ_IFR_HWADDR 1
| #define HAVE_STRUCT_IP_MREQN 1
| #define HAVE_SYS_RESOURCE_H 1
| #define HAVE_DECL_GETRLIMIT 1
| #define HAVE_DECL_SETRLIMIT 1
| #define HAVE_DECL_RLIMIT_STACK 1
| #define HAVE_GETRUSAGE 1
| #define HAVE_SYS_TIMERFD_H 1
| #define HAVE_NETPACKET_PACKET_H 1
| #define HAVE_SCHED_H 1
| #define HAVE_SETNS 1
| #define HAVE_LINUX_TYPES_H 1
| #define HAVE_LINUX_ERRQUEUE_H 1
| #define HAVE_SO_BSDCOMPAT /**/
| #define NO_SA_LEN 1
| #define SIZEOF_CHAR 1
| #define SIZEOF_SHORT 2
| #define SIZEOF_INT 4
| #define SIZEOF_LONG 8
| #define SIZEOF_VOID_P 8
| #define SIZEOF_LONG_LONG 8
| #define SIZEOF_SIZE_T 8
| #define SIZEOF_OFF_T 8
| #define SIZEOF_TIME_T 8
| #define SIZEOF_SUSECONDS_T 8
| #define SIZEOF__FLOAT16 2
| #define ERTS_RESTRICT restrict
| #define ERTS_ENDIANNESS -1
| #define HAVE_FDATASYNC 1
| #define HAVE_SENDFILE 1
| #define HAVE_GETADDRINFO 1
| #define HAVE_GETNAMEINFO 1
| #define HAVE_GETHOSTBYNAME2 1
| #define HAVE_FINITE 1
| #define HAVE_DLOPEN 1
| #define HAVE_PREAD 1
| #define HAVE_PWRITE 1
| #define HAVE_MEMMOVE 1
| #define HAVE_STRERROR 1
| #define HAVE_STRERROR_R 1
| #define HAVE_STRNCASECMP 1
| #define HAVE_LOCALTIME_R 1
| #define HAVE_GMTIME_R 1
| #define HAVE_MPROTECT 1
| #define HAVE_MADVISE 1
| #define HAVE_POSIX_MADVISE 1
| #define HAVE_MMAP 1
| #define HAVE_MREMAP 1
| #define HAVE_MEMCPY 1
| #define HAVE_MEMRCHR 1
| #define HAVE_SBRK 1
| #define HAVE_BRK 1
| #define HAVE_FLOCKFILE 1
| #define HAVE_FSTAT 1
| #define HAVE_STRLCPY 1
| #define HAVE_STRLCAT 1
| #define HAVE_SETSID 1
| #define HAVE_SETLOCALE 1
| #define HAVE_NL_LANGINFO 1
| #define HAVE_POLL 1
| #define HAVE_MLOCKALL 1
| #define HAVE_PPOLL 1
| #define HAVE_VSYSLOG 1
| #define HAVE_INET_PTON 1
| #define HAVE_ISFINITE 1
| #define HAVE_POSIX_MEMALIGN 1
| #define HAVE_WRITEV 1
| #define HAVE_DECL_POSIX2TIME 0
| #define HAVE_DECL_TIME2POSIX 0
| #define HAVE_VPRINTF 1
| #define HAVE_CONFLICTING_FREAD_DECLARATION 1
| #define HAVE_PUTC_UNLOCKED 1
| #define HAVE_FWRITE_UNLOCKED 1
| #define HAVE_OPENPTY 1
| #define HAVE_IFADDRS_H 1
| #define HAVE_NETPACKET_PACKET_H 1
| #define HAVE_SYS_UN_H 1
| #define HAVE_GETIFADDRS 1
| #define HAVE_STRUCT_SOCKADDR_UN_SUN_PATH 1
| #define HAVE_IN6ADDR_ANY 1
| #define HAVE_IN6ADDR_LOOPBACK 1
| #define HAVE_DECL_IN6ADDR_ANY_INIT 1
| #define HAVE_DECL_IN6ADDR_LOOPBACK_INIT 1
| #define HAVE_DECL_IPV6_V6ONLY 1
| #define HAVE_SCHED_xETAFFINITY 1
| #define HAVE_END_SYMBOL 1
| #define HAVE__END_SYMBOL 1
| #define SBRK_RET_TYPE void *
| #define SBRK_ARG_TYPE intptr_t
| #define BRK_RET_TYPE int
| #define BRK_ARG_TYPE void *
| #define ERTS_STRUCTURE_ALIGNED_ALLOC 1
| #define HAVE_IN6 1
| #define HAVE_MULTICAST_SUPPORT 1
| #define HAVE_CLOCK_GETRES 1
| #define HAVE_GETTIMEOFDAY 1
| #define OS_SYSTEM_TIME_USING_CLOCK_GETTIME 1
| #define WALL_CLOCK_ID_STR "CLOCK_REALTIME"
| #define WALL_CLOCK_ID CLOCK_REALTIME
| #define HAVE_CLOCK_GETRES 1
| #define OS_MONOTONIC_TIME_USING_CLOCK_GETTIME 1
| #define ERTS_HAVE_CORRECTED_OS_MONOTONIC_TIME 1
| #define MONOTONIC_CLOCK_ID_STR "CLOCK_MONOTONIC"
| #define MONOTONIC_CLOCK_ID CLOCK_MONOTONIC
| #define HAVE_CLOCK_GETTIME_MONOTONIC_RAW 1
| #define HAVE_CLOCK_GETRES 1
| #define SYS_HRTIME_USING_CLOCK_GETTIME 1
| #define HAVE_MONOTONIC_ERTS_SYS_HRTIME 1
| #define HRTIME_CLOCK_ID_STR "CLOCK_MONOTONIC"
| #define HRTIME_CLOCK_ID CLOCK_MONOTONIC
| #define HAVE_CLOCK_GETTIME_CPU_TIME /**/
| #define NATIVE_ERLANG_STACK /**/
| #define ERLANG_FRAME_POINTERS /**/
| #define HAVE_LINUX_PERF_SUPPORT 1
| #define HAVE_LINUX_THP 1
| /* end confdefs.h.  */
| 
| #include <poll.h>
| main()
| {
| #ifdef _POLL_EMUL_H_
|   exit(1); /* Implemented using select() -- fail */
| #else
|   struct pollfd fds[1];
|   int fd;
|   fd = open("/dev/null", 1);
|   fds[0].fd = fd;
|   fds[0].events = POLLIN;
|   fds[0].revents = 0;
|   if (poll(fds, 1, 0) < 0 || (fds[0].revents & POLLNVAL) != 0) {
|     exit(1);  /* Does not work for devices -- fail */
|   }
|   exit(0);
| #endif
| }
| 
configure:25921: result: no; non-existing, broken, or based on select()

[lukebakken]

Yep, as I expected, on Ubuntu 24 compiler warnings are not treated as errors:

Ubuntu conftest.c compile output

configure:25844: checking for working poll()
configure:25889: x86_64-linux-gnu-gcc -o conftest -fno-strict-aliasing -fno-common -g -O2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -ffile-prefix-map=/usr/local/src/otp-27.2=. -flto=auto -ffat-lto-objects -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -Wl,-rpath=/opt/openssl/lib -I/usr/local/src/otp-27.2/erts/x86_64-pc-linux-gnu   -D_GNU_SOURCE  conftest.c -lutil -ldl -ldl -lm   >&5
conftest.c:265:1: warning: return type defaults to 'int' [-Wimplicit-int]
  265 | main()
      | ^~~~
conftest.c: In function 'main':
conftest.c:272:8: warning: implicit declaration of function 'open' [-Wimplicit-function-declaration]
  272 |   fd = open("/dev/null", 1);
      |        ^~~~
conftest.c:277:5: warning: implicit declaration of function 'exit' [-Wimplicit-function-declaration]
  277 |     exit(1);  /* Does not work for devices -- fail */
      |     ^~~~
conftest.c:265:1: note: include '<stdlib.h>' or provide a declaration of 'exit'
  264 | #include <poll.h>
  +++ |+#include <stdlib.h>
  265 | main()
conftest.c:277:5: warning: incompatible implicit declaration of built-in function 'exit' [-Wbuiltin-declaration-mismatch]
  277 |     exit(1);  /* Does not work for devices -- fail */
      |     ^~~~
conftest.c:277:5: note: include '<stdlib.h>' or provide a declaration of 'exit'
conftest.c:279:3: warning: incompatible implicit declaration of built-in function 'exit' [-Wbuiltin-declaration-mismatch]
  279 |   exit(0);
      |   ^~~~
conftest.c:279:3: note: include '<stdlib.h>' or provide a declaration of 'exit'
configure:25889: $? = 0
configure:25889: ./conftest
configure:25889: $? = 0
configure:25935: result: yes

So, this needs to be addressed in the Erlang source code. We can work around it for now with a patch.

[lukebakken]

AHA, gcc version 14 defaults certain warnings as errors. Alpine 3.21 uses gcc version 14.2.0 while Ubuntu 24 uses version 13.3.0. THIS is why things changed.

https://gcc.gnu.org/gcc-14/porting_to.html

[michaelklishin]

@rstrlcpy this could be a side effect of Erlang/OTP's build system changes or a peculiarity of your specific OS.

Here are the ./configure settings used by this image. As you can easily see in git blame, nothing except for OpenSSL location has changed in years.

@tianon @yosifkit can you folks think of a relevant change in the last few months (since late September 2024)?

[lukebakken]

@rstrlcpy - I have created the following bug report: erlang/otp#9211

Next, I'll see about patching the Erlang source code before compilation to work around this on Alpine.

[michaelklishin]

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