AWS C/C++ packages use non-standard cmake module paths breaking most distributions

[glaubitz]

I am currently packaging aws-c-common, aws-checkums and aws-c-event-stream for openSUSE as these packages are now required for the aws-sdk-cpp which is already part of openSUSE and SLE.

While packaging, I have run into the problem that the cmake configuration in aws-c-event-stream couldn't find AwsCFlags and AwsSanitizers:

[    5s] CMake Error at CMakeLists.txt:17 (include):
[    5s]   include could not find load file:
[    5s] 
[    5s]     AwsCFlags
[    5s] 
[    5s] 
[    5s] CMake Error at CMakeLists.txt:18 (include):
[    5s]   include could not find load file:
[    5s] 
[    5s]     AwsSanitizers
[    5s] 
[    5s] 
[    5s] CMake Error at CMakeLists.txt:54 (aws_set_common_properties):
[    5s]   Unknown CMake command "aws_set_common_properties".
[    5s] 
[    5s] 
[    5s] -- Configuring incomplete, errors occurred!
[    5s] See also "/home/abuild/rpmbuild/BUILD/aws-c-event-stream-0.1.0/build/CMakeFiles/CMakeOutput.log".
[    5s] error: Bad exit status from /var/tmp/rpm-tmp.QpHCox (%build)

A simple workaround fixes the problem for me:

diff -Nru aws-c-event-stream-0.1.0.orig/CMakeLists.txt aws-c-event-stream-0.1.0/CMakeLists.txt
--- aws-c-event-stream-0.1.0.orig/CMakeLists.txt        2018-12-18 04:15:43.000000000 +0100
+++ aws-c-event-stream-0.1.0/CMakeLists.txt     2019-02-08 14:56:12.388040665 +0100
@@ -13,7 +13,7 @@
 cmake_minimum_required (VERSION 3.1)
 project (aws-c-event-stream C)
 
-list(APPEND CMAKE_MODULE_PATH "${CMAKE_INSTALL_PREFIX}/lib/cmake")
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_INSTALL_PREFIX}/lib64/cmake")
 include(AwsCFlags)
 include(AwsSanitizers)
 include(CheckCCompilerFlag)

The proper fix is certainly to use find_library() instead of include() in this case.

[madebr]

Imho, the proper fix would be to only do find_package(aws-c-common REQUIRED).
The aws-c-common-config.cmake file should modify the CMAKE_MODULE_PATH accordingly.
The proper fix is thus in aws-c-common project.
Consumers of aws-c-common will then be able to include the AwsCFlags, AwsSharedLibSetup, AwsFeatureTests, AwsSanitizers and AwsSIMD modules.

[Lectem]

I'm having the same issue here while trying to build on amazon linux 2.

[glaubitz]

FWIW, this issue affects many C/C++ AWS packages.

We currently ship these libraries in openSUSE and they all needed to have their cmake paths patched:

• aws-c-cal
• aws-c-common
• aws-c-event-stream
• aws-c-io
• aws-checksums
• s2n

I also verified on the cmake paths on Debian/Ubuntu and Fedora/RHEL, they also follow the same directory hierarchy as openSUSE, i.e. $LIBDIR/cmake/$PACKAGE.

Using the proper cmake paths also means that this particular hack that I have found in every CMakeLists.txt of all AWS packages so far is no longer necessary:

# This is required in order to append /lib/cmake to each element in CMAKE_PREFIX_PATH
set(AWS_MODULE_DIR "/${CMAKE_INSTALL_LIBDIR}/cmake")
string(REPLACE ";" "${AWS_MODULE_DIR};" AWS_MODULE_PATH "${CMAKE_PREFIX_PATH}${AWS_MODULE_DIR}")
# Append that generated list to the module search path
list(APPEND CMAKE_MODULE_PATH ${AWS_MODULE_PATH})

I'm currently using this patch for all AWS packages and it fixes the cmake path issues for me:

diff -Nru aws-c-event-stream-0.1.6.orig/CMakeLists.txt aws-c-event-stream-0.1.6/CMakeLists.txt
--- aws-c-event-stream-0.1.6.orig/CMakeLists.txt        2020-07-24 02:06:45.000000000 +0200
+++ aws-c-event-stream-0.1.6/CMakeLists.txt     2020-08-25 13:17:04.469790864 +0200
@@ -11,17 +11,11 @@
     file(TO_CMAKE_PATH "${CMAKE_INSTALL_PREFIX}" CMAKE_INSTALL_PREFIX)
 endif()
 
-if (UNIX AND NOT APPLE)
-    include(GNUInstallDirs)
-elseif(NOT DEFINED CMAKE_INSTALL_LIBDIR)
-    set(CMAKE_INSTALL_LIBDIR "lib")
-endif()
+find_package(aws-c-common REQUIRED)
+find_package(aws-checksums REQUIRED)
+set(CMAKE_MODULE_PATH ${aws-c-common_DIR})
 
-# This is required in order to append /lib/cmake to each element in CMAKE_PREFIX_PATH
-set(AWS_MODULE_DIR "/${CMAKE_INSTALL_LIBDIR}/cmake")
-string(REPLACE ";" "${AWS_MODULE_DIR};" AWS_MODULE_PATH "${CMAKE_PREFIX_PATH}${AWS_MODULE_DIR}")
-# Append that generated list to the module search path
-list(APPEND CMAKE_MODULE_PATH ${AWS_MODULE_PATH})
+include(GNUInstallDirs)
 
 include(AwsCFlags)
 include(AwsSharedLibSetup)
@@ -92,7 +86,7 @@
 endif()
 
 install(EXPORT "${PROJECT_NAME}-targets"
-    DESTINATION "${LIBRARY_DIRECTORY}/${PROJECT_NAME}/cmake/${TARGET_DIR}/"
+    DESTINATION "${LIB_INSTALL_DIR}/cmake/${CMAKE_PROJECT_NAME}/${TARGET_DIR}/"
     NAMESPACE AWS::
     COMPONENT Development)
 
@@ -101,7 +95,7 @@
     @ONLY)
 
 install(FILES "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}-config.cmake"
-    DESTINATION "${LIBRARY_DIRECTORY}/${PROJECT_NAME}/cmake/"
+    DESTINATION "${LIB_INSTALL_DIR}/cmake/${CMAKE_PROJECT_NAME}"
     COMPONENT Development)

It's actually a change that was recommend to me by the cmake upstream developers.