与 gcc -lnetsnmp 链接时未定义的引用
Undefined references when linking with gcc -lnetsnmp
我正在尝试在需要 snmp 库的 raspberry pi 上编译和 运行 我的代码。但是，我收到 linking 错误，例如 "undefined reference to 'EVP_DigestUpdate'"。
过去几天我一直在研究这个问题，发现这通常发生在 snmp 找不到 ssl 库 crypto 时，例如，如果你没有在 -lsnmp 之前指定 -lcrypto linking 您的对象，或者当 linker 无法找到 -lcrypto。
但是，在我的 raspberry pi 上，我在 /usr/lib/gcc/arm-linux-gnueabihf 中拥有所有必需的库。
我是这样安装库的：
apt-get install libssl-dev libsnmp-dev libsnmp-base libsnmp30
我用这个命令生成 trap.o：
gcc -c -g -pedantic -Wall -Wshadow -I/home/pi/tests/h -I/usr/include trap.c -o trap.o
I link trap.o 使用此命令的库：
gcc -static -g -pedantic -Wall -Wshadow trap.o -o trap -L/usr/lib/arm-linux-gnueabihf/lib -lcrypto -lpthread -lnetsnmpagent -lnetsnmpmibs -lnetsnmphelpers -lnetsnmp
然后我得到这个错误：
gcc -static -g -pedantic -Wall -Wshadow trap.o -o trap -L/usr/lib/arm-linux-gnueabihf/lib -lcrypto -lpthread -lnetsnmpagent -lnetsnmpmibs -lnetsnmphelpers -lnetsnmp
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_str_to_gid':
(.text+0x1144): warning: Using 'getgrnam' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_str_to_gid':
(.text+0x1154): warning: Using 'endgrent' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_str_to_uid':
(.text+0x10d8): warning: Using 'getpwnam' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_str_to_uid':
(.text+0x10e8): warning: Using 'endpwent' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_getaddrinfo':
(.text+0x4a4): warning: Using 'getaddrinfo' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_gethostbyaddr':
(.text+0x9f8): warning: Using 'gethostbyaddr' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
trap.o: In function `parse_address':
/home/pi/tests/trap.c:56: warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/crt1.o: In function `_start':
/build/glibc-6f8a9a/glibc-2.19/csu/../ports/sysdeps/arm/start.S:119: undefined reference to `main'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_random':
(.text+0x168): undefined reference to `RAND_bytes'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_generate_keyed_hash':
(.text+0x290): undefined reference to `EVP_md5'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_generate_keyed_hash':
(.text+0x2b4): undefined reference to `HMAC'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_generate_keyed_hash':
(.text+0x33c): undefined reference to `EVP_sha1'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x424): undefined reference to `EVP_sha1'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x42c): undefined reference to `EVP_MD_CTX_create'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x438): undefined reference to `EVP_DigestInit'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x448): undefined reference to `EVP_DigestUpdate'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x458): undefined reference to `EVP_DigestFinal'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x468): undefined reference to `EVP_MD_CTX_destroy'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x488): undefined reference to `EVP_md5'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0x86c): undefined reference to `DES_key_sched'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0x8a0): undefined reference to `DES_ncbc_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0x8c4): undefined reference to `DES_ncbc_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0x90c): undefined reference to `AES_set_encrypt_key'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0x948): undefined reference to `AES_cfb128_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0xa74): undefined reference to `DES_key_sched'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0xaac): undefined reference to `DES_ncbc_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_decrypt':
(.text+0xc78): undefined reference to `AES_set_encrypt_key'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_decrypt':
(.text+0xcb0): undefined reference to `AES_cfb128_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_decrypt':
(.text+0xd9c): undefined reference to `DES_key_sched'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_decrypt':
(.text+0xdd0): undefined reference to `DES_cbc_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x74): undefined reference to `EVP_MD_CTX_create'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x98): undefined reference to `EVP_md5'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0xa4): undefined reference to `EVP_DigestInit'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0xe8): undefined reference to `EVP_DigestUpdate'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x10c): undefined reference to `EVP_DigestFinal'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x138): undefined reference to `EVP_MD_CTX_destroy'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x178): undefined reference to `EVP_sha1'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x184): undefined reference to `EVP_DigestInit'
collect2: error: ld returned 1 exit status
会不会是因为我安装的 snmp 库是使用与我环境中的不同的 openssl 版本构建的？我的 libssl-dev 和 libsnmp-dev 版本如下：
dpkg -l | grep libssl-dev:
ii libssl-dev:armhf 1.0.1k-3+deb8u5 armhf Secure Sockets Layer toolkit - development files
dpkg -l | grep libsnmp-dev:
ii libsnmp-dev 5.7.2.1+dfsg-1 armhf SNMP (Simple Network Management Protocol) development files
如有任何帮助，我们将不胜感激，
谢谢
您所有未定义的引用都在 libnetsnmp 中并且它们都是未定义的
对 libcypto 中定义的函数的引用。发生这种情况是因为 -lcrypto
在您的 link 年龄之前 -lnetsnmp。
在linkage序列中，必须出现需要符号定义的文件
在提供定义的那些之前，因为默认情况下 linker 会
仅搜索库以查找它具有的符号定义
观察到在早期文件中被引用，但未定义。 （你似乎
错误地了解了这条规则，错误的方式）。来自 man ld:
The linker will search an archive only once, at the location where
it is specified on the command line. If the archive defines a
symbol which was undefined in some object which appeared before the
archive on the command line, the linker will include the
appropriate file(s) from the archive. However, an undefined symbol
in an object appearing later on the command line will not cause the
linker to search the archive again.
所以 link -lcrypto 在 -lnetsnmp 之后。
我正在尝试在需要 snmp 库的 raspberry pi 上编译和 运行 我的代码。但是，我收到 linking 错误，例如 "undefined reference to 'EVP_DigestUpdate'"。
过去几天我一直在研究这个问题，发现这通常发生在 snmp 找不到 ssl 库 crypto 时，例如，如果你没有在 -lsnmp 之前指定 -lcrypto linking 您的对象，或者当 linker 无法找到 -lcrypto。
但是，在我的 raspberry pi 上，我在 /usr/lib/gcc/arm-linux-gnueabihf 中拥有所有必需的库。
我是这样安装库的：
apt-get install libssl-dev libsnmp-dev libsnmp-base libsnmp30
我用这个命令生成 trap.o：
gcc -c -g -pedantic -Wall -Wshadow -I/home/pi/tests/h -I/usr/include trap.c -o trap.o
I link trap.o 使用此命令的库：
gcc -static -g -pedantic -Wall -Wshadow trap.o -o trap -L/usr/lib/arm-linux-gnueabihf/lib -lcrypto -lpthread -lnetsnmpagent -lnetsnmpmibs -lnetsnmphelpers -lnetsnmp
然后我得到这个错误：
gcc -static -g -pedantic -Wall -Wshadow trap.o -o trap -L/usr/lib/arm-linux-gnueabihf/lib -lcrypto -lpthread -lnetsnmpagent -lnetsnmpmibs -lnetsnmphelpers -lnetsnmp
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_str_to_gid':
(.text+0x1144): warning: Using 'getgrnam' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_str_to_gid':
(.text+0x1154): warning: Using 'endgrent' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_str_to_uid':
(.text+0x10d8): warning: Using 'getpwnam' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_str_to_uid':
(.text+0x10e8): warning: Using 'endpwent' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_getaddrinfo':
(.text+0x4a4): warning: Using 'getaddrinfo' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(system.o): In function `netsnmp_gethostbyaddr':
(.text+0x9f8): warning: Using 'gethostbyaddr' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
trap.o: In function `parse_address':
/home/pi/tests/trap.c:56: warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/crt1.o: In function `_start':
/build/glibc-6f8a9a/glibc-2.19/csu/../ports/sysdeps/arm/start.S:119: undefined reference to `main'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_random':
(.text+0x168): undefined reference to `RAND_bytes'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_generate_keyed_hash':
(.text+0x290): undefined reference to `EVP_md5'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_generate_keyed_hash':
(.text+0x2b4): undefined reference to `HMAC'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_generate_keyed_hash':
(.text+0x33c): undefined reference to `EVP_sha1'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x424): undefined reference to `EVP_sha1'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x42c): undefined reference to `EVP_MD_CTX_create'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x438): undefined reference to `EVP_DigestInit'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x448): undefined reference to `EVP_DigestUpdate'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x458): undefined reference to `EVP_DigestFinal'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x468): undefined reference to `EVP_MD_CTX_destroy'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_hash':
(.text+0x488): undefined reference to `EVP_md5'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0x86c): undefined reference to `DES_key_sched'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0x8a0): undefined reference to `DES_ncbc_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0x8c4): undefined reference to `DES_ncbc_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0x90c): undefined reference to `AES_set_encrypt_key'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0x948): undefined reference to `AES_cfb128_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0xa74): undefined reference to `DES_key_sched'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_encrypt':
(.text+0xaac): undefined reference to `DES_ncbc_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_decrypt':
(.text+0xc78): undefined reference to `AES_set_encrypt_key'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_decrypt':
(.text+0xcb0): undefined reference to `AES_cfb128_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_decrypt':
(.text+0xd9c): undefined reference to `DES_key_sched'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(scapi.o): In function `sc_decrypt':
(.text+0xdd0): undefined reference to `DES_cbc_encrypt'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x74): undefined reference to `EVP_MD_CTX_create'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x98): undefined reference to `EVP_md5'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0xa4): undefined reference to `EVP_DigestInit'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0xe8): undefined reference to `EVP_DigestUpdate'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x10c): undefined reference to `EVP_DigestFinal'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x138): undefined reference to `EVP_MD_CTX_destroy'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x178): undefined reference to `EVP_sha1'
/usr/lib/gcc/arm-linux-gnueabihf/4.9/../../../arm-linux-gnueabihf/libnetsnmp.a(keytools.o): In function `generate_Ku':
(.text+0x184): undefined reference to `EVP_DigestInit'
collect2: error: ld returned 1 exit status
会不会是因为我安装的 snmp 库是使用与我环境中的不同的 openssl 版本构建的？我的 libssl-dev 和 libsnmp-dev 版本如下：
dpkg -l | grep libssl-dev:
ii libssl-dev:armhf 1.0.1k-3+deb8u5 armhf Secure Sockets Layer toolkit - development files
dpkg -l | grep libsnmp-dev:
ii libsnmp-dev 5.7.2.1+dfsg-1 armhf SNMP (Simple Network Management Protocol) development files
如有任何帮助，我们将不胜感激，
谢谢
您所有未定义的引用都在 libnetsnmp 中并且它们都是未定义的
对 libcypto 中定义的函数的引用。发生这种情况是因为 -lcrypto
在您的 link 年龄之前 -lnetsnmp。
在linkage序列中，必须出现需要符号定义的文件
在提供定义的那些之前，因为默认情况下 linker 会
仅搜索库以查找它具有的符号定义
观察到在早期文件中被引用，但未定义。 （你似乎
错误地了解了这条规则，错误的方式）。来自 man ld:
The linker will search an archive only once, at the location where it is specified on the command line. If the archive defines a symbol which was undefined in some object which appeared before the archive on the command line, the linker will include the appropriate file(s) from the archive. However, an undefined symbol in an object appearing later on the command line will not cause the linker to search the archive again.
所以 link -lcrypto 在 -lnetsnmp 之后。