Compile with QUIC_BUILD_SHARED=OFF may failed by linking dl.a

[st-jliu]

Describe the bug

Try compile msquic as static library, it may failed by linking dl.a and file not found

Affected OS

• Windows
• Linux
• macOS
• Other (specify below)

Additional OS information

Docker image ubuntu:20.04

MsQuic version

v2.1

Steps taken to reproduce bug

Use FetchContent to introduce

set(QUIC_BUILD_SHARED   OFF)
include(FetchContent)
FetchContent_Declare(MsQuic
        URL                               "https://github.com/microsoft/msquic/archive/refs/tags/v2.1.8.tar.gz"
        URL_HASH                   "MD5=e620c59dbcfad952a6007b071cc5d5f5"
        )
FetchContent_MakeAvailable(MsQuic)

Expected behavior

Generate libmsquic.a without any error

Actual outcome

[ 34%] Generating ../../../../../../external/msquic/libs/libmsquic.a
/usr/bin/ar: dl.a: No such file or directory
""""""""""make[2]: *** [_deps/msquic-build/src/bin/CMakeFiles/msquic_lib.dir/build.make:77: ../../external/msquic/libs/libmsquic.a] Error 9

Additional details

Compile on ubuntu 20.04 locally or cross compile with Android NDK r23.1 LTS, will all failed by linking dl.a

[st-jliu]

Patch the cmake function flatten_link_dependencies() in src/bin/CMakeLists.txt, skip target 'dl' just like the 'Threads::Threads' can fix it, actually cmake generate static library do not need link with libdl.a nore libdl.so

--- msquic-2.1.8-old/src/bin/CMakeLists.txt	2023-03-16 20:47:31
+++ msquic-2.1.8-new/src/bin/CMakeLists.txt	2023-12-07 11:07:30
@@ -57,12 +57,13 @@
         if(NOT TARGET ${CURRENT_TARGET})
             string(FIND ${CURRENT_TARGET} "$<LINK_ONLY:" LINK_ONLY)
             string(FIND ${CURRENT_TARGET} "Threads::Threads" THREADS_TARGET)
+            string(FIND ${CURRENT_TARGET} "dl" DL_TARGET)
             string(FIND ${CURRENT_TARGET} "${CMAKE_STATIC_LIBRARY_SUFFIX}" SUFFIX_INDEX)
             if(${SUFFIX_INDEX} EQUAL "-1")
                 string(APPEND CURRENT_TARGET "${CMAKE_STATIC_LIBRARY_SUFFIX}")
             endif()

-            if(${LINK_ONLY} EQUAL "-1" AND ${THREADS_TARGET} EQUAL "-1")
+            if(${LINK_ONLY} EQUAL "-1" AND ${THREADS_TARGET} EQUAL "-1" AND ${DL_TARGET} EQUAL "-1")
                 # This is expected to be a generator expression that maps
                 # to a static library
                 set_property(

[nibanks]

Would you be willing to propose a PR?

[st-jliu]

We will try verify on latest release v2.2.4 and main branch, if this issue still exist, we will prepare a PR