[swift-users] how to ``swift build`` C library cleanly without using -Xcc -Xlinker and -Xswiftc

[Martin Man]

Hi Dan,

thanks for your comments… I have prepared a simple module here: https://github.com/mman/cmod1.

``git clone`` and ``swift build`` it and you will see the problem I’m talking about… 

please let me know if you need any help, I’ll prepare a more complex project showing the problem with this module being used as a dependency of another more complex module soon…

thanks,
Martin

> On 20 Oct 2016, at 17:34, Daniel Dunbar <daniel_dunbar at apple.com> wrote:
> 
>> 
>> On Oct 20, 2016, at 7:25 AM, Martin Man via swift-users <swift-users at swift.org <mailto:swift-users at swift.org>> wrote:
>> 
>> Hi guys,
>> 
>> I’m wrapping three little native C libraries using SPM to a nice swifty modules. Say cmod1, cmod2, and cmod3. They all in the and are dependencies of a bigger project.
>> 
>> Since these legacy C libraries have headers in various ways incompatible with SPM I’m also providing my own custom module.modulemap inside of Sources/cmod1/include folder which exports only certain headers.
>> 
>> The module.modulemap is in pretty standard form with relative path to the header
>> 
>> module cmod1 {
>> header “cmod1/header1.h”
>> export “*”
>> link “cmod1"
>> } 
>> 
>> When using ``swift build`` to build the module, C sources compile fine but switc bails out when parsing modulemap because it can not find headers referenced from header1.h with an error message like this
>> 
>> <module-includes>:1:10: note: in file included from <module-includes>:1:
>> #include “/projects/something/Sources/cmod1/include/cmod/header1.h"
> 
> Is this misspelled? cmod/header1.h vs cmod1/header1.h?
> 
> Can you show the exact include style used in the module.modulemap and in the project?
> 
>>          ^
>> /projects/something/Sources/cmod1/include/cmod1/header1.h:18:10: error: ‘cmod1/header2.h' file not found
>> 
>> Now I know that I can give swiftc correct -Xswiftc -Ipath switch and then it builds cleanly, but this means that plain ``swift build`` never succeeds…
>> 
>> Q1: Is my assumption correct that the ultimate goal of mine is to make the swift package build cleanly using just ``swift build`` without providing any commandline flags?
> 
> Yes.
> 
>> Q2: When build of a certain package cmod1 requires command line flags -Xcc -Xlinker and -Xswiftc, what’s the correct way to pass them in when such package is a dependency of bigger project and which gets git pulled and compiled as part of outer package build?
> 
> We don't have a solution for this yet, eventually we want to find a way that all that data has a proper home in the manifest.
> 
>  - Daniel
> 
>> 
>> thanks for your time, unfortunately the sources of these packages can not be made public yet but I think I can generate a simple broken project on github if anyone wants to take a look...
>> 
>> thanks,
>> Martin
>> 
>> 
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