编译PostgreSQL扩展时出现RocksDB链接错误

问题描述 #

我正在尝试基于RocksDB构建PostgreSQL扩展，使用的Makefile如下：

MODULES = pgtam
EXTENSION = pgtam
DATA = pgtam--0.0.1.sql
PG_CPPFLAGS += -I/usr/local/include
SHLIB_LINK += -L/usr/local/lib -lrocksdb -lz -lbz2 -lsnappy -lzstd

PG_CONFIG = /usr/local/pgsql/bin/pg_config
PGXS := $(shell $(PG_CONFIG) --pgxs)
include $(PGXS)

执行make时出现链接错误，具体信息如下：

gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Werror=unguarded-availability-new -Wendif-labels -Wmissing-format-attribute -Wcast-function-type -Wformat-security -fno-strict-aliasing -fwrapv -Wno-unused-command-line-argument -Wno-compound-token-split-by-macro -g -ggdb -Og -g3 -fno-omit-frame-pointer  -fvisibility=hidden -I/usr/local/include -I. -I./ -I/usr/local/pgsql/include/server -I/usr/local/pgsql/include/internal  -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.4.sdk    -c -o pgtam.o pgtam.c
gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Werror=unguarded-availability-new -Wendif-labels -Wmissing-format-attribute -Wcast-function-type -Wformat-security -fno-strict-aliasing -fwrapv -Wno-unused-command-line-argument -Wno-compound-token-split-by-macro -g -ggdb -Og -g3 -fno-omit-frame-pointer  -fvisibility=hidden pgtam.o -L/usr/local/pgsql/lib -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.4.sdk   -Wl,-dead_strip_dylibs   -fvisibility=hidden -bundle -bundle_loader /usr/local/pgsql/bin/postgres -o pgtam.dylib
Undefined symbols for architecture arm64:
  "_rocksdb_get", referenced from:
      _memam_relation_set_new_filelocator in pgtam.o
      _get_table in pgtam.o
      _get_table in pgtam.o
  "_rocksdb_open", referenced from:
      _mem_tableam_handler in pgtam.o
  "_rocksdb_options_create", referenced from:
      _mem_tableam_handler in pgtam.o
  "_rocksdb_options_destroy", referenced from:
      _mem_tableam_handler in pgtam.o
  "_rocksdb_options_optimize_level_style_compaction", referenced from:
      _mem_tableam_handler in pgtam.o
  "_rocksdb_options_set_create_if_missing", referenced from:
      _mem_tableam_handler in pgtam.o
  "_rocksdb_put", referenced from:
      _memam_relation_set_new_filelocator in pgtam.o
      _set_ntables in pgtam.o
  "_rocksdb_readoptions_create", referenced from:
      _memam_relation_set_new_filelocator in pgtam.o
      _get_table in pgtam.o
      _get_table in pgtam.o
  "_rocksdb_readoptions_destroy", referenced from:
      _memam_relation_set_new_filelocator in pgtam.o
      _get_table in pgtam.o
      _get_table in pgtam.o
  "_rocksdb_writeoptions_create", referenced from:
      _memam_relation_set_new_filelocator in pgtam.o
      _set_ntables in pgtam.o
  "_rocksdb_writeoptions_destroy", referenced from:
      _memam_relation_set_new_filelocator in pgtam.o
      _set_ntables in pgtam.o
ld: symbol(s) not found for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [pgtam.dylib] Error 1

我已经确认以下两点：

• /usr/local/lib路径下存在librocksdb.dylib文件
• 该库包含错误提示中缺失的符号，执行nm /usr/local/lib/librocksdb.dylib | rg _rocksdb_get的输出如下：

╰─$ nm /usr/local/lib/librocksdb.dylib | rg _rocksdb_get
00000000000493a4 T _rocksdb_get
00000000000494f8 T _rocksdb_get_cf
000000000004992c T _rocksdb_get_cf_with_ts
0000000000056854 T _rocksdb_get_column_family_metadata
00000000000568cc T _rocksdb_get_column_family_metadata_cf
0000000000049088 T _rocksdb_get_full_history_ts_low
000000000004beb0 T _rocksdb_get_latest_sequence_number
0000000000056598 T _rocksdb_get_options_from_string
000000000005b800 T _rocksdb_get_pinned
000000000005b94c T _rocksdb_get_pinned_cf
000000000004bbd0 T _rocksdb_get_updates_since
0000000000049738 T _rocksdb_get_with_ts

解决方法 #

核心问题是链接库的顺序错误，在链接过程中，被依赖的库需要放在依赖它的库之后。RocksDB依赖各类压缩库，因此需要调整SHLIB_LINK中的参数顺序。

1. 调整Makefile的链接顺序 #

修改SHLIB_LINK行，将-lrocksdb移到所有压缩库之后：

SHLIB_LINK += -L/usr/local/lib -lz -lbz2 -lsnappy -lzstd -lrocksdb

2. 额外验证项 #

• 确认RocksDB库是针对arm64架构编译的：
  执行file /usr/local/lib/librocksdb.dylib，输出应包含arm64标识：

  /usr/local/lib/librocksdb.dylib: Mach-O 64-bit dynamically linked shared library arm64
  

• 确认PostgreSQL也是arm64架构版本：
  执行file /usr/local/pgsql/bin/postgres验证输出中的架构信息。

内容的提问来源于stack exchange，提问作者ACC