CODEWITHSUNDEEP
cmakec99qnx
iwarv
iwarv

Reputation: 449

CMake / QNX 6.5 does not understand gnu99 standard

I have already been made aware of this question, in which the OP seeks to use C++11 standards. And I understand that - regrettably - C++11 is just too new for QNX 6.5. But my question relates to the same compiler and the C99 standard, which is approximately 10 years older than the compiler being used here.

I am converting an existing QNX 6.5 project to CMake. This builds fine(ish) in Momentics, but I am falling at the first hurdle; generating the project.

I have this as my CMake file

cmake_minimum_required(VERSION 3.16)

set(CMAKE_C_STANDARD 99)

project(Analyser)

# other stuff

When I try to generate this using the QNX toolchain I get

The C compiler

    "/opt/qnx650/host/linux/x86/usr/bin/qcc"

  is not able to compile a simple test program.

  It fails with the following output:

    Change Dir: /home/user/build.analyser/CMakeFiles/CMakeTmp
    
    Run Build Command(s):/usr/bin/ninja cmTC_4ee62 && [1/2] Building C object CMakeFiles/cmTC_4ee62.dir/testCCompiler.c.o
    FAILED: CMakeFiles/cmTC_4ee62.dir/testCCompiler.c.o 
    /opt/qnx650/host/linux/x86/usr/bin/qcc -Vgcc_ntoarmle -Wc,-isysroot,/opt/qnx650/target/qnx6   -std=gnu99 -Wp,-MD,CMakeFiles/cmTC_4ee62.dir/testCCompiler.c.o.d -Wp,-MT,CMakeFiles/cmTC_4ee62.dir/testCCompiler.c.o -Wp,-MF,CMakeFiles/cmTC_4ee62.dir/testCCompiler.c.o.d -o CMakeFiles/cmTC_4ee62.dir/testCCompiler.c.o -c /home/user/build.analyser/CMakeFiles/CMakeTmp/testCCompiler.c
    cc: unknown option: -std=gnu99

If I remove the CMAKE_C_STANDARD then the project generates fine, but it does not build because it defaults to C89 I guess.

If I bypass the compiler check (CMAKE_C_COMPILER_WORKS) then of course the project generates fine. But building the code gets me this...

/opt/qnx650/host/linux/x86/usr/bin/qcc -Vgcc_ntoarmle -Wc,-isysroot,/opt/qnx650/target/qnx6  -I{lots of include dirs} -Wc -std=gnu99 -Wp,-MD,syslib/CMakeFiles/syslib.dir/logger.c.o.d -Wp,-MT,syslib/CMakeFiles/syslib.dir/logger.c.o -Wp,-MF,syslib/CMakeFiles/syslib.dir/logger.c.o.d -o syslib/CMakeFiles/syslib.dir/logger.c.o -c /home/user/project/syslib/logger.c
cc: unknown option: -std=gnu99

(not sure why so many options get repeated)

So the cmake compiler check wasn't just a hinderance. The thing is, this works from within Momentics

/opt/qnx650/host/linux/x86/usr/bin/qcc -Vgcc_ntoarm -c -O -Wc,-Wall -pedantic-errors -Wc,-std=gnu99 -DNDEBUG -I{lots of include dirs} -EL -DVARIANT_a -DVARIANT_le -DBUILDENV_qss /home/user/project/syslib/logger.c

I doubt that the other command line options make any difference here for making the compiler understand gnu99 (I've not looked into these yet, but I will), but if you know better then please put me right.

The question comes down to this: What must I do to use the c99 / gnu99 standard in a QNX 6.5 CMake project?

Upvotes: 0

Views: 78

Answers (1)

iwarv
iwarv

Reputation: 449

This document from Blackberry / QNX 6.5 on the qcc compiler interface explains that qcc does not understand the -std argument.

The document suggests we pass certain options to the (cc1) compiler thusly

-W phase,arg[,arg ...]
    Pass the specified option and its arguments through to a specific phase:

        p — preprocessor
        c — compiler
        l — linker
        a — assembler.

So to compile for C99 we should invoke qcc as

qcc -Wc,-std=c99 {other parameters} [source file]

CMake cannot do this for you when you add set(CMAKE_C_STANDARD 99) to your QNX 6.5 based project.
One possible workaround I am working with does...

if (CMAKE_C_COMPILER_VERSION GREATER 4.4.2)
    set(CMAKE_C_STANDARD 99)
else()
    add_compile_options(
        $<$<COMPILE_LANGUAGE:C>:-Wc,-std=gnu99>
    )
endif()

Please note that these instructions apply to QNX 6.5 only!

As of QNX 7, the -std argument is supported by qcc and you should be able to nominate the C standard in the way CMake intended without any of this "fuss".

Upvotes: 0

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