说明: 由于现网的php不带curl功能, 需要编译生成一个libcurl.so给php生成curl.so模块用. 并且需要支持openssl. 编译的过程并不顺利, 这里做下记录备忘.

使用如下configure命令生成配置文件. ssl是提前编译好的openssl.
    ./configure --prefix=/home/nemo/progs/curl --with-ssl=/home/nemo/progs/ssl

问题1编译报错:
Making all in src
make[1]: Entering directory `/data/home/nemo/libs/curl-7.27.0/src'
make  all-am
make[2]: Entering directory `/data/home/nemo/libs/curl-7.27.0/src'
/bin/sh ../libtool --tag=CC --mode=link gcc  -g0 -O2 -Wno-system-headers    -L/home/nemo/progs/ssl/lib -o curl  hugehelp.o tool_binmode.o tool_bname.o tool_cb_dbg.o tool_cb_hdr.o tool_cb_prg.o tool_cb_rea.o tool_cb_see.o tool_cb_wrt.o tool_cfgable.o tool_convert.o tool_dirhie.o tool_doswin.o tool_easysrc.o tool_formparse.o tool_getparam.o tool_getpass.o tool_help.o tool_helpers.o tool_homedir.o tool_libinfo.o tool_main.o tool_metalink.o tool_mfiles.o tool_msgs.o tool_operate.o tool_operhlp.o tool_panykey.o tool_paramhlp.o tool_parsecfg.o tool_setopt.o tool_sleep.o tool_urlglob.o tool_util.o tool_vms.o tool_writeenv.o tool_writeout.o tool_xattr.o strtoofft.o strdup.o rawstr.o nonblock.o  ../lib/libcurl.la -lrt -lz  
libtool: link: gcc -g0 -O2 -Wno-system-headers -o .libs/curl hugehelp.o tool_binmode.o tool_bname.o tool_cb_dbg.o tool_cb_hdr.o tool_cb_prg.o tool_cb_rea.o tool_cb_see.o tool_cb_wrt.o tool_cfgable.o tool_convert.o tool_dirhie.o tool_doswin.o tool_easysrc.o tool_formparse.o tool_getparam.o tool_getpass.o tool_help.o tool_helpers.o tool_homedir.o tool_libinfo.o tool_main.o tool_metalink.o tool_mfiles.o tool_msgs.o tool_operate.o tool_operhlp.o tool_panykey.o tool_paramhlp.o tool_parsecfg.o tool_setopt.o tool_sleep.o tool_urlglob.o tool_util.o tool_vms.o tool_writeenv.o tool_writeout.o tool_xattr.o strtoofft.o strdup.o rawstr.o nonblock.o  -L/home/nemo/progs/ssl/lib ../lib/.libs/libcurl.so -lrt -lz -Wl,-rpath -Wl,/home/nemo/progs/curl/lib
../lib/.libs/libcurl.so: undefined reference to `EVP_enc_null'
../lib/.libs/libcurl.so: undefined reference to `COMP_compress_block'
../lib/.libs/libcurl.so: undefined reference to `COMP_CTX_new'
../lib/.libs/libcurl.so: undefined reference to `SRP_Calc_B'
../lib/.libs/libcurl.so: undefined reference to `BIO_s_socket'
../lib/.libs/libcurl.so: undefined reference to `pqueue_next'
../lib/.libs/libcurl.so: undefined reference to `pqueue_insert'
../lib/.libs/libcurl.so: undefined reference to `SRP_check_known_gN_param'
../lib/.libs/libcurl.so: undefined reference to `COMP_expand_block'
../lib/.libs/libcurl.so: undefined reference to `pqueue_peek'
../lib/.libs/libcurl.so: undefined reference to `SRP_Calc_x'
../lib/.libs/libcurl.so: undefined reference to `pqueue_free'
../lib/.libs/libcurl.so: undefined reference to `OPENSSL_DIR_read'
../lib/.libs/libcurl.so: undefined reference to `SRP_Calc_client_key'
../lib/.libs/libcurl.so: undefined reference to `X509_STORE_set_default_paths'
../lib/.libs/libcurl.so: undefined reference to `COMP_CTX_free'
../lib/.libs/libcurl.so: undefined reference to `pqueue_find'
../lib/.libs/libcurl.so: undefined reference to `pqueue_pop'
../lib/.libs/libcurl.so: undefined reference to `pitem_free'
../lib/.libs/libcurl.so: undefined reference to `SRP_create_verifier_BN'
../lib/.libs/libcurl.so: undefined reference to `SRP_Verify_B_mod_N'
../lib/.libs/libcurl.so: undefined reference to `pqueue_iterator'
../lib/.libs/libcurl.so: undefined reference to `SRP_get_default_gN'
../lib/.libs/libcurl.so: undefined reference to `pqueue_size'
../lib/.libs/libcurl.so: undefined reference to `X509_certificate_type'
../lib/.libs/libcurl.so: undefined reference to `SRP_Calc_server_key'
../lib/.libs/libcurl.so: undefined reference to `SRP_Verify_A_mod_N'
../lib/.libs/libcurl.so: undefined reference to `SRP_Calc_A'
../lib/.libs/libcurl.so: undefined reference to `pqueue_new'
../lib/.libs/libcurl.so: undefined reference to `SRP_Calc_u'
../lib/.libs/libcurl.so: undefined reference to `OPENSSL_DIR_end'
../lib/.libs/libcurl.so: undefined reference to `COMP_zlib'
../lib/.libs/libcurl.so: undefined reference to `ERR_load_crypto_strings'
../lib/.libs/libcurl.so: undefined reference to `X509_STORE_load_locations'
../lib/.libs/libcurl.so: undefined reference to `pitem_new'
collect2: ld returned 1 exit status
make[2]: *** [curl] Error 1
make[2]: Leaving directory `/data/home/nemo/libs/curl-7.27.0/src'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/data/home/nemo/libs/curl-7.27.0/src'
make: *** [all-recursive] Error 1

分析:
1) 这些报错未定义的符号是什么符号? 是属于哪个库的? 是openssl的吗? (可以通过nm ssl的so或库查看)
   经查是, crypto库的
2) 那么crypto库在哪里? 有没有默认链接进来?
   经查是个crypto.a文件, 放在了ssl的编译号的同级目录里 : /home/nemo/progs/ssl/lib/libcrypto.a
   另外, 系统默认也带了crypto :  /usr/local/ssl/lib/libcrypto.a

   另外, 查看编译链接的选项, 指定了对应的目录, -L/home/nemo/progs/ssl/lib
   但是却没有指定 -lcrypto ?!!!
  
   解决: 进入src目录, 手动执行链接命令, 在最后补上 crypto 即可通过.
   /bin/sh ../libtool --tag=CC --mode=link gcc  -g0 -O2 -Wno-system-headers    -L/home/nemo/progs/ssl/lib -o curl  hugehelp.o tool_binmode.o tool_bname.o tool_cb_dbg.o tool_cb_hdr.o tool_cb_prg.o tool_cb_rea.o tool_cb_see.o tool_cb_wrt.o tool_cfgable.o tool_convert.o tool_dirhie.o tool_doswin.o tool_easysrc.o tool_formparse.o tool_getparam.o tool_getpass.o tool_help.o tool_helpers.o tool_homedir.o tool_libinfo.o tool_main.o tool_metalink.o tool_mfiles.o tool_msgs.o tool_operate.o tool_operhlp.o tool_panykey.o tool_paramhlp.o tool_parsecfg.o tool_setopt.o tool_sleep.o tool_urlglob.o tool_util.o tool_vms.o tool_writeenv.o tool_writeout.o tool_xattr.o strtoofft.o strdup.o rawstr.o nonblock.o  ../lib/libcurl.la -lrt -lz -lcrypto

问题2 
发现编译出来的libcurl.so虽然成功编译出来了, 通过ldd -r 查看, 仍然包含了很多未定义的符号, 就像上面的编译curl可执行文件报错的符号一样.
nemo@ISD_36_57_sles10sp1:[curl-7.20.1]$ ldd -r ./lib/.libs/libcurl.so
undefined symbol: X509_certificate_type    (./lib/.libs/libcurl.so)
undefined symbol: COMP_CTX_free    (./lib/.libs/libcurl.so)
undefined symbol: COMP_CTX_new    (./lib/.libs/libcurl.so)
undefined symbol: COMP_compress_block    (./lib/.libs/libcurl.so)
undefined symbol: COMP_expand_block    (./lib/.libs/libcurl.so)
undefined symbol: pqueue_find    (./lib/.libs/libcurl.so)
undefined symbol: pitem_new    (./lib/.libs/libcurl.so)
undefined symbol: pqueue_insert    (./lib/.libs/libcurl.so)
undefined symbol: pqueue_iterator    (./lib/.libs/libcurl.so)
undefined symbol: pqueue_next    (./lib/.libs/libcurl.so)
undefined symbol: pitem_free    (./lib/.libs/libcurl.so)
undefined symbol: pqueue_pop    (./lib/.libs/libcurl.so)
undefined symbol: pqueue_peek    (./lib/.libs/libcurl.so)
undefined symbol: X509_STORE_load_locations    (./lib/.libs/libcurl.so)
undefined symbol: X509_STORE_set_default_paths    (./lib/.libs/libcurl.so)
undefined symbol: BIO_s_socket    (./lib/.libs/libcurl.so)
undefined symbol: ERR_load_crypto_strings    (./lib/.libs/libcurl.so)
undefined symbol: OPENSSL_DIR_read    (./lib/.libs/libcurl.so)
undefined symbol: OPENSSL_DIR_end    (./lib/.libs/libcurl.so)
    linux-gate.so.1 =>  (0xbfffe000)
    librt.so.1 => /lib/librt.so.1 (0xb7cf4000)
    libdl.so.2 => /lib/libdl.so.2 (0xb7cf0000)
    libz.so.1 => /lib/libz.so.1 (0xb7cde000)
    libc.so.6 => /lib/libc.so.6 (0xb7bbd000)
    libpthread.so.0 => /lib/libpthread.so.0 (0xb7ba9000)
    /lib/ld-linux.so.2 (0x80000000)
undefined symbol: COMP_zlib    (./lib/.libs/libcurl.so)
undefined symbol: EVP_enc_null    (./lib/.libs/libcurl.so)
undefined symbol: SRP_Calc_A    (./lib/.libs/libcurl.so)
undefined symbol: SRP_check_known_gN_param    (./lib/.libs/libcurl.so)
undefined symbol: SRP_Verify_B_mod_N    (./lib/.libs/libcurl.so)
undefined symbol: SRP_Calc_u    (./lib/.libs/libcurl.so)
undefined symbol: SRP_Calc_x    (./lib/.libs/libcurl.so)
undefined symbol: SRP_Calc_client_key    (./lib/.libs/libcurl.so)
undefined symbol: SRP_Verify_A_mod_N    (./lib/.libs/libcurl.so)
undefined symbol: SRP_Calc_server_key    (./lib/.libs/libcurl.so)
undefined symbol: SRP_get_default_gN    (./lib/.libs/libcurl.so)
undefined symbol: SRP_create_verifier_BN    (./lib/.libs/libcurl.so)
undefined symbol: SRP_Calc_B    (./lib/.libs/libcurl.so)
undefined symbol: pqueue_free    (./lib/.libs/libcurl.so)
undefined symbol: pqueue_new    (./lib/.libs/libcurl.so)
undefined symbol: pqueue_size    (./lib/.libs/libcurl.so   

分析:
    经过把整个make的成 >make.log 2>&1, 定向到文件里面, 发现make.log有如下可疑的地方.
    ... // 省了好多.
    -L/home/nemo/progs/ssl/lib -lrt -lcrypto -lssl -ldl -lz  -O2   -Wl,-soname -Wl,libcurl.so.4 -o .libs/libcurl.so.4.2.0

    -lcrypto -lssl , crypto居然放在ssl的前面 ? 如果ssl依赖crypto, 应该ssl放在前面才对. 
解决:
    进入lib目录, 修改Makefile
    LIBCURL_LIBS = -lssl -lcrypto -lrt -lcrypto -lssl -ldl -lz  => 
    LIBCURL_LIBS = -lssl -lcrypto -lrt -ldl -lz 即可.

总结, 编译生成curl时, 需手动命令行加入 -lcrypto编译;(改Makefile不管用) 变成生成libcurl.so时, 可以修改Makefile编译.