diff options
| author | fanquake <fanquake@gmail.com> | 2020-04-22 14:32:27 +0800 |
|---|---|---|
| committer | fanquake <fanquake@gmail.com> | 2020-04-22 14:46:19 +0800 |
| commit | 7d1a3bda21214b119c0e6380927d451454669f9f (patch) | |
| tree | 85d82b4303c6f6b47a1f1ca9656e5a50d67d4074 | |
| parent | b6a5dc90bfd4640cf9f914e59bf8e21cd265b51e (diff) | |
| parent | b155fcda5186c59fc4fb2a9eaaf791d132e0ab30 (diff) | |
Merge #18709: doc: note why we can't use thread_local with glibc back compat
b155fcda5186c59fc4fb2a9eaaf791d132e0ab30 doc: fix typo in configure.ac (fanquake)
20a30922fbf6ba14e250ca649239af115dbbe7b0 doc: note why we can't use thread_local with glibc back compat (fanquake)
Pull request description:
Given that we went through a [gitian build](https://github.com/bitcoin/bitcoin/pull/18681) to remember why this is the case, we might as well make a note of it in configure.ac.
[From #18681](https://github.com/bitcoin/bitcoin/pull/18681#issuecomment-615526634):
Looking at the Linux build log, this has failed with:
```bash
Checking glibc back compat...
bitcoind: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
bitcoind: failed IMPORTED_SYMBOLS
bitcoin-cli: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
bitcoin-cli: failed IMPORTED_SYMBOLS
bitcoin-tx: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
bitcoin-tx: failed IMPORTED_SYMBOLS
bitcoin-wallet: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
bitcoin-wallet: failed IMPORTED_SYMBOLS
test/test_bitcoin: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
test/test_bitcoin: failed IMPORTED_SYMBOLS
bench/bench_bitcoin: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
bench/bench_bitcoin: failed IMPORTED_SYMBOLS
qt/bitcoin-qt: symbol __cxa_thread_atexit_impl from unsupported version GLIBC_2.18
```
`__cxa_thread_atexit_impl` is used for [thread_local variable destruction](https://sourceware.org/glibc/wiki/Destructor%20support%20for%20thread_local%20variables):
> To implement this support, glibc defines __cxa_thread_atexit_impl exclusively for use by libstdc++ (which has the __cxa_thread_atexit to wrap around it), that registers destructors for thread_local variables in a list. Upon thread or process exit, the destructors are called in reverse order in which they were added.
As suggested, this only became available in glibc 2.18. From the [2.18 release notes](https://sourceware.org/legacy-ml/libc-alpha/2013-08/msg00160.html):
> * Add support for calling C++11 thread_local object destructors on thread
and program exit. This needs compiler support for offloading C++11
destructor calls to glibc.
ACKs for top commit:
hebasto:
ACK b155fcda5186c59fc4fb2a9eaaf791d132e0ab30
Tree-SHA512: 5b9567e4a70598a4b0b91956f44ae0d93091db17c84cbf9817dac6cfa992c97d3438a8b1bb66644c74891f2149e44984daed445d22de93ca8858c5b0eabefb40
| -rw-r--r-- | configure.ac | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/configure.ac b/configure.ac index 693db0644d..546d00de1b 100644 --- a/configure.ac +++ b/configure.ac @@ -256,7 +256,7 @@ AC_ARG_ENABLE([gprof], [enable_gprof=$enableval], [enable_gprof=no]) -dnl Pass compiler & liner flags that make builds deterministic +dnl Pass compiler & linker flags that make builds deterministic AC_ARG_ENABLE([determinism], [AS_HELP_STRING([--enable-determinism], [Enable compilation flags that make builds deterministic (default is no)])], @@ -861,6 +861,9 @@ AC_LINK_IFELSE([AC_LANG_SOURCE([ ] ) +dnl thread_local is currently disabled when building with glibc back compat. +dnl Our minimum supported glibc is 2.17, however support for thread_local +dnl did not arrive in glibc until 2.18. if test "x$use_thread_local" = xyes || { test "x$use_thread_local" = xauto && test "x$use_glibc_compat" = xno; }; then TEMP_LDFLAGS="$LDFLAGS" LDFLAGS="$TEMP_LDFLAGS $PTHREAD_CFLAGS" |