Dynamic-Linking
使用 cmake 與 libldap 的奇怪連結問題
我正在嘗試使用 download_an_compile.sh 腳本（使用 CMake 建構二進製文件）從 FlightGear 項目建構 SimGear。到目前為止建構進展順利，但是當腳本嘗試將建構的目標文件連結到一個庫時，我得到了很多
//usr/lib/x86_64-linux-gnu/libldap_r-2.4.so.2: warning: undefined reference to ber_...@OPENLDAP-2.4_2（其中 … 是每條消息的不同函式名稱）。
-DCMAKE_CXX_STANDARD_LIBRARIES="-llber-2.4"現在我想我只需通過添加到 CMake 的參數來手動指示 CMake 將 lber 庫連結到正在建構的庫。這導致/usr/bin/ld: -llber-2.4 could not be found這對我來說是個謎，因為它就在那裡：
$ ls /usr/lib/x86_64-linux-gnu | grep lber liblber-2.4.so.2 liblber-2.4.so.2.10.8事實上，我不應該得到
undefined reference錯誤，因為這些功能都在那裡：$ nm /usr/lib/x86_64-linux-gnu/liblber-2.4.so.2 $ nm -D /usr/lib/x86_64-linux-gnu/liblber-2.4.so.2 | grep ber 0000000000005fe0 T ber_alloc 0000000000005fa0 T ber_alloc_t 0000000000006d50 T ber_bprint 0000000000007ec0 T ber_bvarray_add 0000000000007df0 T ber_bvarray_add_x 0000000000007cd0 T ber_bvarray_dup_x 0000000000007cc0 T ber_bvarray_free 0000000000007c30 T ber_bvarray_free_x 0000000000007830 T ber_bvdup 0000000000007700 T ber_bvecadd 0000000000007650 T ber_bvecadd_x 0000000000007640 T ber_bvecfree 00000000000075c0 T ber_bvecfree_x 00000000000075b0 T ber_bvfree 0000000000007570 T ber_bvfree_x 0000000000007c20 T ber_bvreplace 0000000000007b80 T ber_bvreplace_x 0000000000002c70 T ber_decode_oid 0000000000006fc0 T ber_dump 0000000000006000 T ber_dup 0000000000007820 T ber_dupbv 0000000000007710 T ber_dupbv_x 0000000000004cc0 T ber_encode_oid 0000000000006ab0 T ber_errno_addr 0000000000006a30 T ber_error_print 0000000000003a80 T ber_first_element 0000000000006250 T ber_flatten 0000000000006170 T ber_flatten2 0000000000005f90 T ber_flush 0000000000005db0 T ber_flush2 0000000000005d70 T ber_free 0000000000005d10 T ber_free_buf 00000000000038d0 T ber_get_bitstringa 0000000000003a70 T ber_get_boolean 0000000000003150 T ber_get_enum 0000000000003080 T ber_get_int 0000000000006400 T ber_get_next 0000000000003a20 T ber_get_null 0000000000007ed0 T ber_get_option 0000000000003730 T ber_get_stringa 0000000000003810 T ber_get_stringal 00000000000037a0 T ber_get_stringa_null 0000000000003160 T ber_get_stringb 00000000000031f0 T ber_get_stringbv 0000000000003650 T ber_get_stringbv_null 0000000000002e30 T ber_get_tag 0000000000006380 T ber_init 00000000000060c0 T ber_init2 0000000000006160 T ber_init_w_nullc 000000000020d168 B ber_int_errno_fn 000000000020d178 B ber_int_log_proc 000000000020d190 B ber_int_memory_fns 000000000020d1a0 B ber_int_options 0000000000009590 T ber_int_sb_close 0000000000009610 T ber_int_sb_destroy 0000000000009500 T ber_int_sb_init 0000000000009710 T ber_int_sb_read 00000000000099e0 T ber_int_sb_write 00000000000069d0 T ber_len 0000000000006f70 T ber_log_bprint 00000000000070b0 T ber_log_dump 0000000000007120 T ber_log_sos_dump 0000000000007a50 T ber_mem2bv 0000000000007950 T ber_mem2bv_x 0000000000007460 T ber_memalloc 0000000000007400 T ber_memalloc_x 00000000000074d0 T ber_memcalloc 0000000000007470 T ber_memcalloc_x 0000000000007390 T ber_memfree 0000000000007330 T ber_memfree_x 0000000000007560 T ber_memrealloc 00000000000074e0 T ber_memrealloc_x 00000000000073f0 T ber_memvfree 00000000000073a0 T ber_memvfree_x 0000000000003b00 T ber_next_element 0000000000002e80 T ber_peek_element 0000000000002fd0 T ber_peek_tag 0000000000005370 T ber_printf 00000000000069e0 T ber_ptrlen 0000000000005080 T ber_put_berval 0000000000005100 T ber_put_bitstring 0000000000005290 T ber_put_boolean 0000000000004f30 T ber_put_enum 0000000000004f50 T ber_put_int 0000000000005220 T ber_put_null 0000000000004f70 T ber_put_ostring 0000000000005350 T ber_put_seq 0000000000005360 T ber_put_set 00000000000050b0 T ber_put_string 000000000020d170 B ber_pvt_err_file 0000000000006ad0 T ber_pvt_log_output 000000000020d008 D ber_pvt_log_print 0000000000006c20 T ber_pvt_log_printf 000000000020d1e0 B ber_pvt_opt_on 0000000000008f00 T ber_pvt_sb_buf_destroy 0000000000008ee0 T ber_pvt_sb_buf_init 0000000000009180 T ber_pvt_sb_copy_out 00000000000093b0 T ber_pvt_sb_do_write 0000000000008fe0 T ber_pvt_sb_grow_buffer 00000000000094c0 T ber_pvt_socket_set_nonblock 0000000000005a20 T ber_read 0000000000005ad0 T ber_realloc 0000000000006a20 T ber_remaining 00000000000062f0 T ber_reset 00000000000069f0 T ber_rewind 0000000000003ba0 T ber_scanf 00000000000080f0 T ber_set_option 00000000000059a0 T ber_skip_data 0000000000002f90 T ber_skip_element 0000000000003020 T ber_skip_tag 0000000000008d30 T ber_sockbuf_add_io 0000000000009560 T ber_sockbuf_alloc 0000000000009800 T ber_sockbuf_ctrl 00000000000096a0 T ber_sockbuf_free 000000000020d060 D ber_sockbuf_io_debug 000000000020d0a0 D ber_sockbuf_io_fd 000000000020d0e0 D ber_sockbuf_io_readahead 000000000020d120 D ber_sockbuf_io_tcp 000000000020d020 D ber_sockbuf_io_udp 0000000000008e20 T ber_sockbuf_remove_io 0000000000007130 T ber_sos_dump 00000000000069c0 T ber_start 0000000000005310 T ber_start_seq 0000000000005330 T ber_start_set 0000000000007940 T ber_str2bv 0000000000007840 T ber_str2bv_x 0000000000007ac0 T ber_strdup 0000000000007a60 T ber_strdup_x 0000000000007b70 T ber_strndup 0000000000007b10 T ber_strndup_x 0000000000007ad0 T ber_strnlen 0000000000005c00 T ber_write
ldd還表明libldap正在引用正確的liblber：$ ldd /usr/lib/x86_64-linux-gnu/libldap_r-2.4.so.2 | grep lber liblber-2.4.so.2 => /usr/lib/x86_64-linux-gnu/liblber-2.4.so.2 (0x00007f28c8bdc000)有沒有人有任何想法？我沒有……如果我忘記了任何細節，請告訴我，我會添加它們！
至少在 Debian（及其衍生產品）中，共享庫的開發文件被拆分為單獨的二進制包：
如果有共享庫關聯的開發文件，源碼包需要生成一個名為 libraryname-dev 的二進制開發包，或者如果需要一次支持多個開發版本， librarynameapiversion-dev。安裝開發包必須導致安裝針對該共享庫編譯程序所需的所有開發文件。
在這種情況下，“開發文件”主要是指 C/C++ 標頭檔，但重要的是通常包含指向共享庫本身的符號連結
開發包應包含關聯共享庫的符號連結，沒有版本號。例如，libgdbm-dev 包應該包含一個從 /usr/lib/libgdbm.so 到 libgdbm.so.3.0.0 的符號連結。編譯包時連結器 (ld) 需要此符號連結，因為它只會在動態編譯時查找 libgdbm.so。
在這種情況下，儘管您已經擁有共享庫
liblber-2.4.so.2 liblber-2.4.so.2.10.8在
/usr/lib/x86_64-linux-gnu但似乎沒有符號連結/usr/lib/x86_64-linux-gnu/liblber.so，這是由相應的開發包提供的libldap2-dev。