[Bug c++/12401] New: G++ generates boguous weak definition of library routine

[Bug c++/12401] New: G++ generates boguous weak definition of library routine

[uddeborg at carmen dot se]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12401

           Summary: G++ generates boguous weak definition of library routine
           Product: gcc
           Version: 3.2.3
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: uddeborg at carmen dot se
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-redhat-linux
  GCC host triplet: i386-redhat-linux
GCC target triplet: i386-redhat-linux

When compiling some code referencing library routines, the generated object file
 contains a "W" definition of this library routine.

1.Create a file c.cc containing
  #include <stdlib.h>

  int f()
  {
    return atoi <= 0;
  }
2. g++ -O -c c.cc
3. nm -gC c.o
    
This produces:
00000000 W atoi
         U __strtol_internal
00000000 T f()

I would expect an "U atoi" instead of the first two.

This occurs on Red Hat Enterprise Linux beta Taroon 2.  gcc-c++-3.2.3-19

Witout optimization, one gets the expected result.

One problem this behaviour cases occurs is the object file is placed in an
archive library.  If an application which links with this library uses, in this
case, atoi(), then this object file will be included in the end result.  Even if
there are no "real" references to it.  Which of course means any constructors of
global objects, or other side effects of its inclusion, will also happen.

[Bug c++/12401] G++ generates boguous weak definition of library routine

[nathan at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12401


nathan at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


------- Additional Comments From nathan at gcc dot gnu dot org  2003-09-25 12:29 -------
confirmed, this is a duplicate of (part of) 12291 wrt extern inline handling

*** This bug has been marked as a duplicate of 12291 ***

[Bug c++/12401] G++ generates boguous weak definition of library routine

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-25 03:21 -------
This is unrelated to bug 12291.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|DUPLICATE                   |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12401

[Bug c++/12401] G++ generates boguous weak definition of library routine

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-25 03:27 -------
Simple testcase: 
extern inline void Foo () {}
static void Baz () { Foo (); }
This is not a regression.
Confirmed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2003-12-25 03:27:27
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12401

[Bug c++/12401] G++ generates boguous weak definition of library routine

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-25 03:33 -------
Even 2.91.6 does this.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12401

[Bug c++/12401] G++ generates boguous weak definition of library routine

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2003-12-25 04:10 -------
Acutally "extern inline" in C++ is difference that GCC's c extesion "extern inline", "extern inline" in 
C++ means that the function is extern but is declared in all translation unit as inline.

>From the C++ standard:
7.1.2 Function specifiers
4 An inline function shall be defined in every translation unit in which it is used and shall have 
exactly the same definition in every case (3.2). [Note:a call to the inline function may be 
encountered before its definition appears in the translation unit. ] If a function with external 
linkage is declared inline in one translation unit, it shall be declared inline in all translation units in 
which it appears; no diagnostic is required. An inlinefunction with external linkage shall have the 
same address in all translation units. Astatic local variable in anextern inlinefunction always refers 
to the same object. A string literal in an extern inlinefunction is the same object in different 
translation units. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12401

[Bug c++/12401] G++ generates boguous weak definition of library routine

[uddeborg at carmen dot se]

------- Additional Comments From uddeborg at carmen dot se  2004-01-14 16:56 -------
I understand what you say about extern inline in C++.  But note that my original
example did not include any explicit such definition.  Also note that no weak
definition is generated if a file (translation unit) is compiled without
optimization.  (Maybe to simplify debugging.)  Let me give a slightly bigger
example to illustrate the problem:

Create a file e.cc which contains a use of atoi, and some object with a side
effect in the constructor:

   #include <cstdlib>
   #include <iostream>

   int f() { return atoi <= 0; }

   class sideeffect
   {
   public:
     sideeffect() { std::cout << "Unwanted side effect." << std::endl; }
   } s;

and a main program in f.cc which uses atoi:

   #include <cstdlib>
   #include <iostream>
   int main() { std::cout << atoi("5") << std::endl; return 0; }

Now compile e.cc with optimization and put it in an archive library:

   c++ -c -O e.cc
   ar r libe.a e.o

Compile the main program without optimization, and link with this library:

   c++ f.cc -o f libe.a

Running this will have the "unwanted side effect" printed out.  I believe the
program itself meets all requirements in the C++ standard.  The standard does
not go into such things as optimization flags.  So if one wants to be picky I
guess one could argue the same set of flags should be applied to all translation
units.

But is this really a desired behaviour?  I found the effects quite surprising
and counter-intuitive, until I understood what was going on.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12401

[Bug c++/12401] G++ generates boguous weak definition of library routine

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-01-14 17:35 -------
You example does via the glibc headers, they are not wrong, not GCC.  The problem with the 
unwantted side effect is wrong, you cannot depend on if something does not get pulled in or not 
pulled.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12401

[Bug c++/12401] G++ generates boguous weak definition of library routine

[uddeborg at carmen dot se]

------- Additional Comments From uddeborg at carmen dot se  2004-01-15 07:52 -------
Ok.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |VERIFIED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12401