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digitalmars.D.learn - Building application with LDC and -flto=thin fails in link stage

reply =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:
When I try build my application using LDC and -flto=thin it fails 
in the final linking as

ldmd2 
-of.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE
A959C2B7F/knetquery .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE6A
59C2B7F/knetquery.o ../../.dub/packages/gmp-d-master/gmp-d/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-0CE08DAF93E48445402E07C
537FA4E6/libgmp-d.a phobos-next/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-933571CC843E8D13926CEC14051E7195/l
bknet_phobos-next.a -L--no-as-needed -L-lzstd -L-lgmp -L-lc -L-lreadline -L-lz
-L-lbz2
/usr/bin/ld: error: 
.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE6A959C2
7F/knetquery.o:1:3: invalid character
/usr/bin/ld: error: 
.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE6A959C2
7F/knetquery.o:1:3: syntax error, unexpected $end
/usr/bin/ld: error: 
.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2E324E9DAE6A9
9C2B7F/knetquery.o: not an object or archive
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o:function
_start: error: undefined reference to 'main'
collect2: error: ld returned 1 exit status
Error: /usr/bin/gcc failed with status: 1
FAIL 
.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-9FDE475789CA2
324E9DAE6A959C2B7F/ knetquery executable
ldmd2 failed with exit code 1.

What could be wrong?
Mar 26 2018
next sibling parent reply Johan Engelen <j j.nl> writes:
On Monday, 26 March 2018 at 22:07:49 UTC, Nordlöw wrote:

 When I try build my application using LDC and -flto=thin it 
 fails in the final linking


You must also pass `-flto=thin` during linking (a special plugin 
is needed for LTO, and LDC will only pass the plugin to the 
linker when `-flto=` is specified).
I couldn't see `-flto=thin` in your link command, so I suspect 
that will fix it.

- Johan
Mar 26 2018
parent reply =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:
On Monday, 26 March 2018 at 22:13:02 UTC, Johan Engelen wrote:

 On Monday, 26 March 2018 at 22:07:49 UTC, Nordlöw wrote:

 When I try build my application using LDC and -flto=thin it 
 fails in the final linking


 You must also pass `-flto=thin` during linking (a special 
 plugin is needed for LTO, and LDC will only pass the plugin to 
 the linker when `-flto=` is specified).
 I couldn't see `-flto=thin` in your link command, so I suspect 
 that will fix it.

 - Johan


I added `lflags` to my dub configuration as

buildType "release-nobounds-lto" {
          buildOptions "releaseMode" "optimize" "inline" 

          dflags "-mcpu=native" "-O3" "-flto=thin" 
platform="posix-ldc"
          lflags "-flto=thin" platform="posix-ldc"
}

forwarded as `-L-flto=thin` but still errors as

Linking...
ldmd2 
-of.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C
B0B23442E/knetquery .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B
B23442E/knetquery.o ../../.dub/packages/gmp-d-master/gmp-d/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-B287F67CE5FF6145BC22979
CFB09607/libgmp-d.a phobos-next/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F0F2FDB01B8401C04D657BCC145D46A5/l
bknet_phobos-next.a -L--no-as-needed -L-flto=thin -L-lzstd -L-lgmp -L-lc
-L-lreadline -L-lz -L-lbz2
/usr/bin/ld: error: 
.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B0B234
2E/knetquery.o:1:3: invalid character
/usr/bin/ld: error: 
.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B0B234
2E/knetquery.o:1:3: syntax error, unexpected $end
/usr/bin/ld: error: 
.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B0
23442E/knetquery.o: not an object or archive
/usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/Scrt1.o:function
_start: error: undefined reference to 'main'
collect2: error: ld returned 1 exit status
Error: /usr/bin/gcc failed with status: 1
FAIL 
.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA2
7C077E5C2B0B23442E/ knetquery executable
ldmd2 failed with exit code 1.
Mar 26 2018
parent reply kinke <kinke libero.it> writes:
On Monday, 26 March 2018 at 23:32:59 UTC, Nordlöw wrote:

 forwarded as `-L-flto=thin` but still errors as


Which is wrong, it's not a ld command-line option (i.e., the `-L` 
prefix is wrong). I don't use dub though, so I don't know how to 
fix it.
Mar 27 2018
parent reply Johan Engelen <j j.nl> writes:
On Tuesday, 27 March 2018 at 13:28:08 UTC, kinke wrote:

 On Monday, 26 March 2018 at 23:32:59 UTC, Nordlöw wrote:

 forwarded as `-L-flto=thin` but still errors as


 Which is wrong, it's not a ld command-line option (i.e., the 
 `-L` prefix is wrong).


Indeed.
Please try to manually link first (without dub) by modifying the 
command on which dub errors:

```
ldmd2 -flto=thin 
-of.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C
B0B23442E/knetquery .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B
B23442E/knetquery.o ../../.dub/packages/gmp-d-master/gmp-d/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-B287F67CE5FF6145BC22979
CFB09607/libgmp-d.a phobos-next/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F0F2FDB01B8401C04D657BCC145D46A5/l
bknet_phobos-next.a -L--no-as-needed -L-lzstd -L-lgmp -L-lc -L-lreadline -L-lz
-L-lbz2
```

-Johan
Mar 27 2018
parent reply Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:
On Tuesday, 27 March 2018 at 22:00:42 UTC, Johan Engelen wrote:

 Indeed.
 Please try to manually link first (without dub) by modifying 
 the command on which dub errors:

 ```
 ldmd2 -flto=thin 
 -of.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C
B0B23442E/knetquery .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B
B23442E/knetquery.o ../../.dub/packages/gmp-d-master/gmp-d/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-B287F67CE5FF6145BC22979
CFB09607/libgmp-d.a phobos-next/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F0F2FDB01B8401C04D657BCC145D46A5/l
bknet_phobos-next.a -L--no-as-needed -L-lzstd -L-lgmp -L-lc -L-lreadline -L-lz
-L-lbz2
 ```

 -Johan


Yes, that works!
Mar 27 2018
parent reply Johan Engelen <j j.nl> writes:
On Tuesday, 27 March 2018 at 22:10:33 UTC, Per Nordlöw wrote:

 On Tuesday, 27 March 2018 at 22:00:42 UTC, Johan Engelen wrote:

 Indeed.
 Please try to manually link first (without dub) by modifying 
 the command on which dub errors:

 ```
 ldmd2 -flto=thin 
 -of.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C
B0B23442E/knetquery .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B
B23442E/knetquery.o ../../.dub/packages/gmp-d-master/gmp-d/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-B287F67CE5FF6145BC22979
CFB09607/libgmp-d.a phobos-next/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F0F2FDB01B8401C04D657BCC145D46A5/l
bknet_phobos-next.a -L--no-as-needed -L-lzstd -L-lgmp -L-lc -L-lreadline -L-lz
-L-lbz2
 ```

 -Johan


 Yes, that works!


Good :-)

I'm no dub expert and I don't know how to pass flags to the 
_compiler_ for the link step.
Would be good to figure that out with the dub folks.

There will be similar problems with using ASan (and fuzzer 
aswell):  `-fsanitize=address` must also be passed to the D 
compiler (not the linker) during linking such that the correct 
asan library is linked into the executable.

- Johan
Mar 28 2018
next sibling parent reply Seb <seb wilzba.ch> writes:
On Wednesday, 28 March 2018 at 16:42:23 UTC, Johan Engelen wrote:

 On Tuesday, 27 March 2018 at 22:10:33 UTC, Per Nordlöw wrote:

 On Tuesday, 27 March 2018 at 22:00:42 UTC, Johan Engelen wrote:

 Indeed.
 Please try to manually link first (without dub) by modifying 
 the command on which dub errors:

 ```
 ldmd2 -flto=thin 
 -of.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C
B0B23442E/knetquery .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B
B23442E/knetquery.o ../../.dub/packages/gmp-d-master/gmp-d/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-B287F67CE5FF6145BC22979
CFB09607/libgmp-d.a phobos-next/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F0F2FDB01B8401C04D657BCC145D46A5/l
bknet_phobos-next.a -L--no-as-needed -L-lzstd -L-lgmp -L-lc -L-lreadline -L-lz
-L-lbz2
 ```

 -Johan


 Yes, that works!


 Good :-)

 I'm no dub expert and I don't know how to pass flags to the 
 _compiler_ for the link step.
 Would be good to figure that out with the dub folks.

 There will be similar problems with using ASan (and fuzzer 
 aswell):  `-fsanitize=address` must also be passed to the D 
 compiler (not the linker) during linking such that the correct 
 asan library is linked into the executable.

 - Johan


dub supports dflags and lflags in the config file. lflags are the 
linker commands.

http://code.dlang.org/package-format?lang=sdl#build-settings

You can also specify per platform arguments, e.g.

dflags "-version=BuildingWithLDCRocks" platform="ldc"

(dub even supports the environment variables DFLAGS which dmd 
doesn't (and of course LFLAGS))
Mar 28 2018
parent reply Johan Engelen <j j.nl> writes:
On Wednesday, 28 March 2018 at 17:03:07 UTC, Seb wrote:

 
 dub supports dflags and lflags in the config file. lflags are 
 the linker commands.


Please read the thread.

`lflags` is for passing flags to the _linker_ (i.e. those flags 
are prefixed with -L when passed to the _compiler_)

Here, what's needed is passing flags to the _compiler_ when it is 
invoked to perform the link step in the build.

-Johan
Mar 28 2018
parent reply Jacob Carlborg <doob me.com> writes:
On Wednesday, 28 March 2018 at 20:09:24 UTC, Johan Engelen wrote:

 On Wednesday, 28 March 2018 at 17:03:07 UTC, Seb wrote:

 
 dub supports dflags and lflags in the config file. lflags are 
 the linker commands.


 Please read the thread.

 `lflags` is for passing flags to the _linker_ (i.e. those flags 
 are prefixed with -L when passed to the _compiler_)

 Here, what's needed is passing flags to the _compiler_ when it 
 is invoked to perform the link step in the build.


Please read the reply :), although it could be a bit more clear.

`dflags` is used to pass arbitrary flags to the compiler. See the 
bottom of the table at [1].

[1] https://code.dlang.org/package-format?lang=sdl#build-settings

--
/Jacob Carlborg
Mar 29 2018
parent Johan Engelen <j j.nl> writes:
On Thursday, 29 March 2018 at 08:44:21 UTC, Jacob Carlborg wrote:

 Please read the reply :), although it could be a bit more clear.


I'll spell it out for you.

Both `dflags` and `lflags` are being used already. With separate 
compilation and linking, there seems to be no way to pass flags 
to the compiler during the linking step: dflags is not used and 
lflags is prefixed with `-L`.

-Johan
Mar 30 2018
prev sibling parent Johan Engelen <j j.nl> writes:
On Wednesday, 28 March 2018 at 16:42:23 UTC, Johan Engelen wrote:

 On Tuesday, 27 March 2018 at 22:10:33 UTC, Per Nordlöw wrote:

 On Tuesday, 27 March 2018 at 22:00:42 UTC, Johan Engelen wrote:

 Indeed.
 Please try to manually link first (without dub) by modifying 
 the command on which dub errors:

 ```
 ldmd2 -flto=thin 
 -of.dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C
B0B23442E/knetquery .dub/build/application-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F2904BE3C4DA237C077E5C2B
B23442E/knetquery.o ../../.dub/packages/gmp-d-master/gmp-d/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-B287F67CE5FF6145BC22979
CFB09607/libgmp-d.a phobos-next/.dub/build/library-release-nobounds-lto-linux.posix-x86_64-ldc_2078-F0F2FDB01B8401C04D657BCC145D46A5/l
bknet_phobos-next.a -L--no-as-needed -L-lzstd -L-lgmp -L-lc -L-lreadline -L-lz
-L-lbz2
 ```

 -Johan


 Yes, that works!


 I'm no dub expert and I don't know how to pass flags to the 
 _compiler_ for the link step.
 Would be good to figure that out with the dub folks.


For a stopgap solution:
I think what you are doing is passing 
`--compiler=<yourpath>/ldmd2` (note: LDMD) to dub when building, 
and you get separate compilation+linking. If you'd use 
`--compiler=<yourpath>/ldc2` (note: LDC), then you would not get 
separate compilation+linking [1] and things work with just 
setting `dflags`.

I've asked about the problem here: 
https://github.com/dlang/dub/issues/1431

cheers,
   Johan

[1] https://github.com/dlang/dub/issues/809
Mar 30 2018
prev sibling parent Arek <arychlinski gmail.com> writes:
On Monday, 26 March 2018 at 22:07:49 UTC, Nordlöw wrote:

 When I try build my application using LDC and -flto=thin it 
 fails in the final linking as


According to LDC's Release info:

Known issues:
ThinLTO may not work well with the ld.bfd linker, use ld.gold 
instead (-linker=gold).


Maybe this is the problem.

Arek
Mar 27 2018