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digitalmars.D.learn - fPIC Error

reply Dlang User <dlang.user gmx.com> writes:
I am running Debian Testing and I think I have run into the 
recent fPIC issue.  This is the source code for the test project 
I am using:

import std.stdio;

void main()
{
	writeln("Edit source/app.d to start your project.");
	readln();
}


When I try to compile a project, I get the following errors 
(truncated for brevity):


/usr/bin/ld: 
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libphobos2.
(thread_26c_155.o): relocation R_X86_64_32 against symbol
`__dmd_personality_v0' can not be used when making a shared object; recompile
with -fPIC
/usr/bin/ld: final link failed: Nonrepresentable section on output
collect2: error: ld returned 1 exit status
dmd failed with exit code 1.
Exit code 2
Build complete -- 1 error, 0 warnings

I followed the advice to add "-defaultlib=libphobos2.so -fPIC" to 
my dmd.conf file as a workaround.

This causes it to build without errors, but now the resulting 
executable is marked as a shared library:

Output of the file command:

fpictest: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), 
dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for 
GNU/Linux 2.6.32, 
BuildID[sha1]=e83ac1d5dea9e78912a6175d3c1c54b50b4e29cd, not 
stripped

Is this a known issue with this workaround or is there some other 
setting that I need to change?
Nov 02 2016
next sibling parent reply rikki cattermole <rikki cattermole.co.nz> writes:
Took me a while to replicate your build environment but it looks like a 
false alarm.

rikki debian:/tmp/test$ dmd test.d
rikki debian:/tmp/test$ file test
test: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), 
dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for 
GNU/Linux 2.6.32, 
BuildID[sha1]=0a6394b9ec9b82e07440ab62cd71932f0ab568d1, not stripped

rikki debian:/tmp/test$ ./test
Edit source/app.d to start your project.

rikki debian:/tmp/test$ cat /etc/dmd.conf
;
; dmd.conf file for dmd
;
; dmd will look for dmd.conf in the following sequence of directories:
;   - current working directory
;   - directory specified by the HOME environment variable
;   - directory dmd resides in
;   - /etc directory
;
; Names enclosed by %% are searched for in the existing environment and 
inserted
;
; The special name % P% is replaced with the path to this file
;

[Environment32]
DFLAGS=-I/usr/include/dmd/phobos -I/usr/include/dmd/druntime/import 
-L-L/usr/lib/i386-linux-gnu -L--export-dynamic -fPIC 
-defaultlib=libphobos2.so

[Environment64]
DFLAGS=-I/usr/include/dmd/phobos -I/usr/include/dmd/druntime/import 
-L-L/usr/lib/x86_64-linux-gnu -L--export-dynamic -fPIC 
-defaultlib=libphobos2.so
Nov 02 2016
next sibling parent dlang user <dlang.user gmx.com> writes:
On Thursday, 3 November 2016 at 06:11:48 UTC, rikki cattermole 
wrote:

 Took me a while to replicate your build environment but it 
 looks like a false alarm.

 rikki debian:/tmp/test$ dmd test.d
 rikki debian:/tmp/test$ file test
 test: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), 
 dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, 
 for GNU/Linux 2.6.32, 
 BuildID[sha1]=0a6394b9ec9b82e07440ab62cd71932f0ab568d1, not 
 stripped

 rikki debian:/tmp/test$ ./test
 Edit source/app.d to start your project.

 rikki debian:/tmp/test$ cat /etc/dmd.conf
 ;
 ; dmd.conf file for dmd
 ;
 ; dmd will look for dmd.conf in the following sequence of 
 directories:
 ;   - current working directory
 ;   - directory specified by the HOME environment variable
 ;   - directory dmd resides in
 ;   - /etc directory
 ;
 ; Names enclosed by %% are searched for in the existing 
 environment and inserted
 ;
 ; The special name % P% is replaced with the path to this file
 ;

 [Environment32]
 DFLAGS=-I/usr/include/dmd/phobos 
 -I/usr/include/dmd/druntime/import -L-L/usr/lib/i386-linux-gnu 
 -L--export-dynamic -fPIC -defaultlib=libphobos2.so

 [Environment64]
 DFLAGS=-I/usr/include/dmd/phobos 
 -I/usr/include/dmd/druntime/import 
 -L-L/usr/lib/x86_64-linux-gnu -L--export-dynamic -fPIC 
 -defaultlib=libphobos2.so


Thanks for looking at it and confirming you are seeing the same 
thing.

I am no expert, but after some additional research I think I see 
what is going on.  From what I read the gcc -fPIC option creates 
a shared library, while gcc -fPIE option creates an executable.  
You can also create a dual purpose file that is a shared library 
and is also executable by creating a shared library if that file 
also contains a main function (that might be oversimplified a 
little bit).

Looking at the dmd documentation, it only has a -fPIC option, 
there is no -fPIE option, which has the following description:

generate Position Independent Code (which is used for building 
shared libraries).

So, if I am understanding everything correctly because dmd only 
has -fPIC, the only option is to create a dual purpose file that 
is both a shared library and executable.
Nov 03 2016
prev sibling parent reply deadalnix <deadalnix gmail.com> writes:
On Thursday, 3 November 2016 at 06:11:48 UTC, rikki cattermole 
wrote:

 [Environment32]
 DFLAGS=-I/usr/include/dmd/phobos 
 -I/usr/include/dmd/druntime/import -L-L/usr/lib/i386-linux-gnu 
 -L--export-dynamic -fPIC -defaultlib=libphobos2.so

 [Environment64]
 DFLAGS=-I/usr/include/dmd/phobos 
 -I/usr/include/dmd/druntime/import 
 -L-L/usr/lib/x86_64-linux-gnu -L--export-dynamic -fPIC 
 -defaultlib=libphobos2.so


I'm sorry bit that's horseshit. I'm not compiling everything with 
fPIC because DMD can't get it's act straight.
Nov 18 2016
parent reply Charles Hixson via Digitalmars-d-learn writes:
On 11/18/2016 10:35 PM, deadalnix via Digitalmars-d-learn wrote:

 On Thursday, 3 November 2016 at 06:11:48 UTC, rikki cattermole wrote:

 [Environment32]
 DFLAGS=-I/usr/include/dmd/phobos -I/usr/include/dmd/druntime/import 
 -L-L/usr/lib/i386-linux-gnu -L--export-dynamic -fPIC 
 -defaultlib=libphobos2.so

 [Environment64]
 DFLAGS=-I/usr/include/dmd/phobos -I/usr/include/dmd/druntime/import 
 -L-L/usr/lib/x86_64-linux-gnu -L--export-dynamic -fPIC 
 -defaultlib=libphobos2.so


 I'm sorry bit that's horseshit. I'm not compiling everything with fPIC 
 because DMD can't get it's act straight.


IIRC, LDC didn't have that problem.  I don't remember testing gdc. But, 
yes, it is quite annoying.
Nov 19 2016
parent Matthias Klumpp <mak debian.org> writes:
On Saturday, 19 November 2016 at 21:14:47 UTC, Charles Hixson 
wrote:

 [...]
 IIRC, LDC didn't have that problem.  I don't remember testing 
 gdc. But, yes, it is quite annoying.


That's because we can maintain those compilers with the 
distribution and configure them appropriately to compile with 
hardening flags and integrate properly with the distro.
GDC is an issue here, since AFAIK it doesn't support PIC yet, so 
for GDC - if it works - there will be some kind of workaround in 
place (telling the linker to not assume PIC code, I guess).
DMD has issues because it's a 3rd-party product - ideally, the 
compiler should be adjusted to output PIC code by default.
You can find more information on this change at 
https://wiki.debian.org/Hardening/PIEByDefaultTransition
Nov 19 2016
prev sibling parent Picaud Vincent <picaud.vincent gmail.com> writes:
On Thursday, 3 November 2016 at 05:16:11 UTC, Dlang User wrote:

 I am running Debian Testing and I think I have run into the 
 recent fPIC issue.  This is the source code for the test 
 project I am using:

 import std.stdio;

 void main()
 {
 	writeln("Edit source/app.d to start your project.");
 	readln();
 }


 When I try to compile a project, I get the following errors 
 (truncated for brevity):


 /usr/bin/ld: 
 /usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libphobos2.
(thread_26c_155.o): relocation R_X86_64_32 against symbol
`__dmd_personality_v0' can not be used when making a shared object; recompile
with -fPIC
 /usr/bin/ld: final link failed: Nonrepresentable section on 
 output
 collect2: error: ld returned 1 exit status
 dmd failed with exit code 1.
 Exit code 2
 Build complete -- 1 error, 0 warnings


I got the same problem, still under Debian. A fix is to use these 
flags:

dmd -shared -m64 -fPIC -defaultlib=libphobos2.so app.d

You can also use another compiler:

dub --compiler=ldc2

or

rdmd --compiler=ldc2

Note that it is not recommended to use gdc because it is not up 
to date, use dmd or ldc2.

Also note, that if you use Emacs + Org Mode,

http://orgmode.org/worg/org-contrib/babel/languages/ob-doc-C.html

you will encounter the same problem. A fix is to add the 
following line in your .emacs file:

(setq org-babel-D-compiler "rdmd --compiler=ldc2")


Vincent
Nov 19 2016