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digitalmars.D - Linking C & extern(C) on OS X: duplicate symbols not flagged

reply =?UTF-8?B?Ikx1w61z?= Marques" <luis luismarques.eu> writes:
On Linux, the following gives out a "multiple definition" error, 
as expected:

     c/test.c:
     void dotest(void) { printf("C\n"); }

     d/test.d:
     extern(C) void dotest() { writeln("D"); }

On OS X no error is flagged, and the C function is always called, 
irrespective of which order I specify the .o files to link. Yet, 
compiling and linking two .c files with a duplication symbol does 
give an error on the linking phase, as expected. So why the 
discrepancy? I'm guessing the cause is the section where the 
symbols appear:

On Ubuntu:

     $ nm d/test.o | grep dotest; echo "--"; nm c/test.o | grep 
dotest
     0000000000000000 T dotest
     --
     0000000000000000 T dotest

On OS X:

     $ nm d/test.o | grep dotest; echo "--"; nm c/test.o | grep 
dotest
     0000000000001490 S _dotest   <-- not in text section, as in 
Linux
     --
     0000000000000000 T _dotest
     0000000000000060 S _dotest.eh

As you might imagine, this situation can be highly disruptive 
(I'm progressively converting a C application to D). Do you know 
why the functions appear in the S section on OS X? Do you know of 
any workaround, to assure that duplicate symbols are correctly 
flagged?
Aug 29 2013
next sibling parent reply Jacob Carlborg <doob me.com> writes:
On 2013-08-30 00:04, "Luís Marques" <luis luismarques.eu>" wrote:
 On Linux, the following gives out a "multiple definition" error, as
 expected:

      c/test.c:
      void dotest(void) { printf("C\n"); }

      d/test.d:
      extern(C) void dotest() { writeln("D"); }

 On OS X no error is flagged, and the C function is always called,
 irrespective of which order I specify the .o files to link. Yet,
 compiling and linking two .c files with a duplication symbol does give
 an error on the linking phase, as expected. So why the discrepancy? I'm
 guessing the cause is the section where the symbols appear:

 On Ubuntu:

      $ nm d/test.o | grep dotest; echo "--"; nm c/test.o | grep dotest
      0000000000000000 T dotest
      --
      0000000000000000 T dotest

 On OS X:

      $ nm d/test.o | grep dotest; echo "--"; nm c/test.o | grep dotest
      0000000000001490 S _dotest   <-- not in text section, as in Linux
      --
      0000000000000000 T _dotest
      0000000000000060 S _dotest.eh

 As you might imagine, this situation can be highly disruptive (I'm
 progressively converting a C application to D). Do you know why the
 functions appear in the S section on OS X? Do you know of any
 workaround, to assure that duplicate symbols are correctly flagged?

How does it behave on Mac OS X if you just use C? -- /Jacob Carlborg
Aug 29 2013
parent reply Jacob Carlborg <doob me.com> writes:
On 2013-08-30 16:10, "Luís Marques" <luis luismarques.eu>" wrote:

 That fails, as expected.

So DMD and Clang uses different sections? Have you tried GDC or LDC? -- /Jacob Carlborg
Aug 31 2013
parent Jacob Carlborg <doob me.com> writes:
On 2013-09-04 00:36, "Luís Marques" <luis luismarques.eu>" wrote:

 Sorry for the delay.

 Using LDC fails, as expected / desired:

      duplicate symbol _dotest in:
          d/test.o
          c/test.o
      ld: 1 duplicate symbol for architecture x86_64

 The LDC .o sections are the same as the C version:

      $ nm d/test.o | grep dotest; echo "--"; nm c/test.o | grep dotest
      0000000000000000 T _dotest
      00000000000000b0 S _dotest.eh
      --
      0000000000000000 T _dotest
      0000000000000060 S _dotest.eh

 I haven't tried GDC (I get the object.d not found error, even after
 installing the D .dmg package, instead of using brew, and I don't recall
 how I used to solve that), but I imagine it would also fail-work (detect
 the duplicate symbol, and fail compilation).

Perhaps time to file a bug report. I don't know if there's a reason to not use the same sections as C does. http://d.puremagic.com/issues/ -- /Jacob Carlborg
Sep 03 2013
prev sibling next sibling parent =?UTF-8?B?Ikx1w61z?= Marques" <luis luismarques.eu> writes:
On Friday, 30 August 2013 at 06:37:07 UTC, Jacob Carlborg wrote:
 How does it behave on Mac OS X if you just use C?

That fails, as expected. (I tried to explain that, I'm sorry if I wasn't clear: )
 On OS X no error is flagged, and the C function is always 
 called, irrespective of which order I specify the .o files to 
 link. Yet, compiling and linking two .c files with a 
 duplication symbol does give an error on the linking phase, as 
 expected.


Aug 30 2013
prev sibling next sibling parent =?UTF-8?B?Ikx1w61z?= Marques" <luis luismarques.eu> writes:
On Saturday, 31 August 2013 at 11:16:11 UTC, Jacob Carlborg wrote:
 So DMD and Clang uses different sections? Have you tried GDC or 
 LDC?

Sorry for the delay. Using LDC fails, as expected / desired: duplicate symbol _dotest in: d/test.o c/test.o ld: 1 duplicate symbol for architecture x86_64 The LDC .o sections are the same as the C version: $ nm d/test.o | grep dotest; echo "--"; nm c/test.o | grep dotest 0000000000000000 T _dotest 00000000000000b0 S _dotest.eh -- 0000000000000000 T _dotest 0000000000000060 S _dotest.eh I haven't tried GDC (I get the object.d not found error, even after installing the D .dmg package, instead of using brew, and I don't recall how I used to solve that), but I imagine it would also fail-work (detect the duplicate symbol, and fail compilation).
Sep 03 2013
prev sibling next sibling parent =?UTF-8?B?Ikx1w61z?= Marques" <luis luismarques.eu> writes:
On Wednesday, 4 September 2013 at 06:36:24 UTC, Jacob Carlborg 
wrote:
 Perhaps time to file a bug report. I don't know if there's a 
 reason to not use the same sections as C does.

I posted it here hoping Walter might comment on this. Maybe he had a good reason to choose a different section. I'll wait a while, and if no feedback is given ("it really has to be a different section because X, Y, Z"), I'll post a bug report.
Sep 04 2013
prev sibling parent =?UTF-8?B?Ikx1w61z?= Marques" <luis luismarques.eu> writes:
On Wednesday, 4 September 2013 at 12:41:52 UTC, Luís Marques 
wrote:
 I posted it here hoping Walter might comment on this. Maybe he 
 had a good reason to choose a different section. I'll wait a 
 while, and if no feedback is given ("it really has to be a 
 different section because X, Y, Z"), I'll post a bug report.

Since Walter did not comment on this, I posted a bug: http://d.puremagic.com/issues/show_bug.cgi?id=11199 I didn't see DMD v2.063.2 in the list of DMD versions, so I chose D2 in the bug report.
Oct 08 2013