Using CCurl in a Kitura based app produces linker errors on Linux only

[dsperling]

In an attempt to use CCurl to develop an SMTP client in Swift, I ran into this problem where the inline functions in shim.h produce linker errors on Linux. macOS works fine.

Functions such as curlHelperSetOptString and curlHelperSetOptInt work fine inside Kitura, but when they are used in an app, a multiple definition of 'curlHelperSetOptString' error occurs.

The functions are defined as inline in shim.h so I am not sure why the compiler is creating a symbol.

Attached is a HelloWorld Kitura based sample app that demonstrates the problem. Tun run execute:

HelloWorld.zip

docker-compose up

I have tried a few changes such as changing "extern inline" to "inline", or moving the declarations to a 'C' file but these cause different issues.

Error output:

test_1  | Compile Swift Module 'LoggerAPI' (1 sources)
test_1  | Compile Swift Module 'Socket' (3 sources)
test_1  | Compile Swift Module 'SwiftyJSON' (2 sources)
test_1  | Compile Swift Module 'KituraTemplateEngine' (1 sources)
test_1  | Compile CHttpParser utils.c
test_1  | clang: warning: argument unused during compilation: '-Xcc'
test_1  | Compile CHttpParser http_parser.c
test_1  | Compile Swift Module 'KituraSys' (3 sources)
test_1  | clang: warning: argument unused during compilation: '-Xcc'
test_1  | Linking CHttpParser
test_1  | Compile Swift Module 'KituraNet' (12 sources)
test_1  | Compile Swift Module 'Kitura' (35 sources)
test_1  | Compile Swift Module 'HelloWorld' (1 sources)
test_1  | Linking .build/debug/HelloWorld
test_1  | /usr/bin/ld.gold: error: /test/.build/debug/KituraNet.build/ClientRequest.swift.o: multiple definition of 'curlHelperSetOptInt'
test_1  | /usr/bin/ld.gold: /test/.build/debug/HelloWorld.build/main.swift.o: previous definition here
test_1  | /usr/bin/ld.gold: error: /test/.build/debug/KituraNet.build/ClientRequest.swift.o: multiple definition of 'curlHelperSetOptList'
test_1  | /usr/bin/ld.gold: /test/.build/debug/HelloWorld.build/main.swift.o: previous definition here
test_1  | /usr/bin/ld.gold: error: /test/.build/debug/KituraNet.build/ClientRequest.swift.o: multiple definition of 'curlHelperSetOptReadFunc'
test_1  | /usr/bin/ld.gold: /test/.build/debug/HelloWorld.build/main.swift.o: previous definition here
test_1  | /usr/bin/ld.gold: error: /test/.build/debug/KituraNet.build/ClientRequest.swift.o: multiple definition of 'curlHelperSetOptString'
test_1  | /usr/bin/ld.gold: /test/.build/debug/HelloWorld.build/main.swift.o: previous definition here
test_1  | clang: error: linker command failed with exit code 1 (use -v to see invocation)
test_1  | <unknown>:0: error: link command failed with exit code 1 (use -v to see invocation)
test_1  | <unknown>:0: error: build had 1 command failures
test_1  | swift-build: error: exit(1): /root/swift-DEVELOPMENT-SNAPSHOT-2016-06-06-a-ubuntu15.10/usr/bin/swift-build-tool -f /test/.build/debug.yaml
helloworld_test_1 exited with code 1

[dsperling]

PR #8 should fix this. I will retest and close.

[dsperling]

Fixed in PR #8