www.digitalmars.com         C & C++   DMDScript  

digitalmars.D - Why D needs a C compiler?

reply rempas <rempas tutanota.com> writes:
To me big surprise, I tried to compile my program after changing 
the "/bin/cc" link from "gcc" to "tcc" and I got an error saying: 
`tcc: error: unsupported linker option '--gc-sections'`.

I haven't noticed that D needs a C compiler before. Why is that 
and why the TinyC compiler (tcc) cannot be used and more 
importantly, can we fix that?
Aug 03 2021
parent reply Paul Backus <snarwin gmail.com> writes:
On Tuesday, 3 August 2021 at 12:59:49 UTC, rempas wrote:

 To me big surprise, I tried to compile my program after 
 changing the "/bin/cc" link from "gcc" to "tcc" and I got an 
 error saying: `tcc: error: unsupported linker option 
 '--gc-sections'`.

 I haven't noticed that D needs a C compiler before. Why is that 
 and why the TinyC compiler (tcc) cannot be used and more 
 importantly, can we fix that?


By default, the D compiler uses `cc` to invoke the linker. You 
can override this by setting the environment variable `CC` (on 
Posix) [1] or `LINKCMD64` (on Windows) [2].

Alternatively, you can compiler your D modules separately with 
`dmd -c` and then invoke the linker directly to build the final 
executable (or have your build system do this).

[1] https://dlang.org/dmd-linux.html#environment
[2] https://dlang.org/dmd-windows.html#environment
Aug 03 2021
parent rempas <rempas tutanota.com> writes:
On Tuesday, 3 August 2021 at 13:54:25 UTC, Paul Backus wrote:

 On Tuesday, 3 August 2021 at 12:59:49 UTC, rempas wrote:

 To me big surprise, I tried to compile my program after 
 changing the "/bin/cc" link from "gcc" to "tcc" and I got an 
 error saying: `tcc: error: unsupported linker option 
 '--gc-sections'`.

 I haven't noticed that D needs a C compiler before. Why is 
 that and why the TinyC compiler (tcc) cannot be used and more 
 importantly, can we fix that?


 By default, the D compiler uses `cc` to invoke the linker. You 
 can override this by setting the environment variable `CC` (on 
 Posix) [1] or `LINKCMD64` (on Windows) [2].

 Alternatively, you can compiler your D modules separately with 
 `dmd -c` and then invoke the linker directly to build the final 
 executable (or have your build system do this).

 [1] https://dlang.org/dmd-linux.html#environment
 [2] https://dlang.org/dmd-windows.html#environment


Thanks for the info! Alright, I'm exporting the "CC" env variable 
to "tcc" and still it will give me the error. I also tried to set 
it to a linker (bot ld and lld) and I'm getting the following 
errors:

```
ld.lld: error: unknown argument '-fuse-ld=ld'
ld.lld: error: unknown argument '-Wl,--gc-sections'
ld.lld: error: unknown emulation: 64
ld.lld: error: unable to find library -lrt
ld.lld: error: unable to find library -ldl
ld.lld: error: unable to find library -lpthread
ld.lld: error: unable to find library -lm
Error: /bin/ld.lld failed with status: 1
```

I used the "--help" option with ldc and it seems that there is an 
option to set the linker ("--linker"), to pass options to the 
linker ("-L") and an option to set the C compiler ("--gcc"). I'm 
setting it up with the following command: `./bin/ldc2 test.d 
--link-internally --linker=ld.lld -L="-L=/usr/lib64" -L"-lc"`. 
However I'm still getting the HUGE following error message:

```
lld: error: undefined symbol: _Unwind_Resume

 referenced by curl.d
               
 curl.o:(_D4core8internal8lifetime__T10emplaceRefTS3std11concurrency__T4ListTSQBbQBa7MessageZQw4NodeTQBz
QBcZQCuFKQCmKQBpZv) in archive /usr/lib64/libphobos2-ldc.a
 referenced by object.d
               
 object.o:(_D6object9Throwable8toStringMxFMDFIAaZvZv) in 
 archive /usr/lib64/libdruntime-ldc.a
 referenced by osthread.d
               
 osthread.o:(_D4core6thread8osthread6Thread5startMFNbZCQBoQBmQBiQBc) in archive
/usr/lib64/libdruntime-ldc.a
 referenced 108 more times






lld: error: undefined symbol: _Unwind_DeleteException

 referenced by dwarfeh.d
               dwarfeh.o:(_d_eh_enter_catch) in archive 
 /usr/lib64/libdruntime-ldc.a
 referenced by dwarfeh.d
               dwarfeh.o:(_d_eh_personality_common) in archive 
 /usr/lib64/libdruntime-ldc.a
 referenced by dwarfeh.d
               dwarfeh.o:(_d_eh_personality_common) in archive 
 /usr/lib64/libdruntime-ldc.a






lld: error: undefined symbol: _Unwind_RaiseException

 referenced by dwarfeh.d
               dwarfeh.o:(_d_throw_exception) in archive 
 /usr/lib64/libdruntime-ldc.a






lld: error: undefined symbol: _Unwind_GetLanguageSpecificData

 referenced by dwarfeh.d
               dwarfeh.o:(_d_eh_personality_common) in archive 
 /usr/lib64/libdruntime-ldc.a






lld: error: undefined symbol: _Unwind_GetRegionStart

 referenced by dwarfeh.d
               dwarfeh.o:(_d_eh_personality_common) in archive 
 /usr/lib64/libdruntime-ldc.a






lld: error: undefined symbol: _Unwind_GetIPInfo

 referenced by dwarfeh.d
               dwarfeh.o:(_d_eh_personality_common) in archive 
 /usr/lib64/libdruntime-ldc.a






lld: error: undefined symbol: _Unwind_SetGR

 referenced by dwarfeh.d
               dwarfeh.o:(_d_eh_personality_common) in archive 
 /usr/lib64/libdruntime-ldc.a
 referenced by dwarfeh.d
               dwarfeh.o:(_d_eh_personality_common) in archive 
 /usr/lib64/libdruntime-ldc.a






lld: error: undefined symbol: _Unwind_SetIP

 referenced by dwarfeh.d
               dwarfeh.o:(_d_eh_personality_common) in archive 
 /usr/lib64/libdruntime-ldc.a






Error: linking with LLD failed
```

If I don't link the "libc", I will only get the error about the 
"_Unwind_Resume" symbol but I will get other for "printf", "free" 
etc. So yeah can anyone help?
Aug 03 2021