Linking statically OpenSSL crypto library in CMake

Question

I want to statically link the libraries listed below:

set_target_properties(exec PROPERTIES LINK_SEARCH_START_STATIC 1)
set_target_properties(exec PROPERTIES LINK_SEARCH_END_STATIC 1)
set(CMAKE_FIND_LIBRARY_SUFFIXES .a ${CMAKE_FIND_LIBRARY_SUFFIXES})

find_library(SODIUM_LIB libsodium.a REQUIRED)
find_library(SSL_LIB libssl.a REQUIRED)
find_library(CRYPTO_LIB libcrypto.a REQUIRED)
find_library(DL_LIB libdl.a REQUIRED)

message(${SODIUM_LIB})
message(${SSL_LIB})
message(${CRYPTO_LIB})

set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -static-libgcc -static-libstdc++")

target_link_libraries(
    exec
    ${SODIUM_LIB}
    ${SSL_LIB}
    ${CRYPTO_LIB}
    ${DL_LIB}

I do not want to add -static to CMAKE_EXE_LINKER_FLAGS, because in that case everything is linked static. CMake finds the static libraries:

/usr/local/lib/libsodium.a
/usr/lib/x86_64-linux-gnu/libssl.a
/usr/lib/x86_64-linux-gnu/libcrypto.a

and it seems that everything is linked statically except libcrypto:

readelf -d exec
 0x0000000000000001 (NEEDED)             Shared library: [libcrypto.so.1.0.0]
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
 0x0000000000000001 (NEEDED)             Shared library: [ld-linux-x86-64.so.2]

How can I link libcrypto statically to my executable?

Unionize

have you checked you actually find the right library? Also it may help to optionally define the path where the static library is to be found. – Fossiliferous

Answer 1

The CMake documentation starting with version 3.4 on the FindOpenSSL page says:

Set OPENSSL_USE_STATIC_LIBS to TRUE to look for static libraries.

(Assuming if they are found they will be used)

Example:

cmake_minimum_required(VERSION 3.4)
project(Foo)

set(SOURCE_FILES main.cpp)

set(OPENSSL_USE_STATIC_LIBS TRUE)
find_package(OpenSSL REQUIRED)

add_executable(${PROJECT_NAME} ${SOURCE_FILES})
target_link_libraries(${PROJECT_NAME} OpenSSL::Crypto)

Jacqulynjactation

As stated by @Tsyvarev in the comments, OPENSSL_USE_STATIC_LIBS is an hint in finding libraries and should prepend find_package(OpenSSL). Verified in FindOpenSSL.cmake source, edited accordingly. – Koreykorff

"should prepend" -> "should come before". Prepend is the opposite of append. In any case, things don't prepend things, let alone themselved. Things are prepended to other things. – Separative

@Separative Both of the examples on dictionary.cambridge.org/dictionary/english/prepend use prepend in the active voice. – Nestorius

@Nestorius Yes, active voice when A is prepending B to C, not when D "is prepending" itself to E. – Separative

bickering aside, "precede" seems more clear to me. "prepend" almost implies concatenation – Ceremonial