[Bug c++/34749] New: Incorrect warning when applying dllimport to friend function

[sldev327 at softmagi dot com]

I was playing with some code and got a warning about dllimport in some
headers.  I looked around a bit and came up with this test case.

The warning seems to imply that dllimport is ignored on bar(), but looking at
the output the call to bar() is indeed mangled with __imp prefix.

I'm using MinGW g++ 4.2.1-dw2.

## begin df.cpp
__attribute__((dllimport)) int bar();

class Foo
{
private:
int foo();
friend __attribute__((dllimport)) int bar();
};

int Foo::foo()
{
return bar();
}
## end df.cpp

D:> g++ -S df.cpp
df.cpp:7: warning: 'int bar()' redeclared without dllimport attribute:
previous dllimport ignored

D:> g++ -v
Using built-in specs.
Target: mingw32
Configured with: ../gcc-4.2.1-2-src/configure --with-gcc
--enable-libgomp --host =mingw32 --build=mingw32 --target=mingw32
--program-suffix=-dw2 --with-arch=i486 --with-tune=generic
--disable-werror --prefix=/mingw --with-local-prefix=/mingw
--enable-threads --disable-nls --enable-languages=c,c+
+,fortran,objc,obj-c++,ad a --disable-win32-registry
--disable-sjlj-exceptions --enable-libstdcxx-debug --
enable-cxx-flags=-fno-function-sections -fno-data-sections
--enable-version-spec ific-runtime-libs --disable-bootstrap Thread
model: win32 gcc version 4.2.1-dw2 (mingw32-2)


-- 
   Summary: Incorrect warning when applying dllimport to friend
function
   Product: gcc
   Version: 4.2.1
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
    ReportedBy: sldev327 at softmagi dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34749

[Bug c++/34749] Incorrect warning when applying dllimport to friend function

[sldev327 at softmagi dot com]

--- Comment #2 from sldev327 at softmagi dot com  2008-01-13 05:52 ---
I as well will leave the argument about syntax to more knowledgeable people.

As to the validity of this PR, at the very least g++'s behavior is
inconsistent.I suppose a case like df3.cpp is what the warning was intended
for.

g++ warns about __attribute__((dllimport)) not being there on line 7 of df.cpp
(when in truth it is), and then goes on to honor it anyway as you can see
comparing the output df.s and df3.s.

## begin df3.cpp
__attribute__((dllimport)) int bar();

class Foo
{
private:
int foo();
friend int bar();  // dllimport removed
};

int Foo::foo()
{
return bar();
}
# end df3.cpp

D:> g++ -S df3.cpp
df3.cpp:7: warning: 'int bar()' redeclared without dllimport attribute:
previous dllimport ignored

D:> diff -u df.s df3.s
--- df.sSun Jan 13 14:02:58 2008
+++ df3.s   Sun Jan 13 14:04:51 2008
@@ -1,4 +1,4 @@
-   .file   "df.cpp"
+   .file   "df3.cpp"
.text
.align 2
 .globl __ZN3Foo3fooEv
@@ -11,8 +11,7 @@
 LCFI1:
subl$8, %esp
 LCFI2:
-   movl__imp___Z3barv, %eax
-   call*%eax
+   call__Z3barv
leave
ret
 LFE2:
@@ -55,3 +54,4 @@
.uleb128 0x5
.align 4
 LEFDE1:
+   .def__Z3barv;   .scl2;  .type   32; .endef


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34749