The C++ code below demonstrates how gcc treats an instance of a temporary as a
variable declaration instead. Without ugly syntax work-arounds, it is not
possible to instantiate the temporary.
[ Code Begins ]------------------------
struct Obj
{
int a ;
} ;
typedef Obj * Obj_P ;
class Foo
{
public :
inline Foo (Obj_P obj_p) : obj_p (obj_p)
{
}
private :
Obj_P obj_p ;
} ;
//--------------------------------------------------------------------------//
int main (void)
{
Obj_P obj_p = 0 ;
Foo (obj_p) ; // Error - Attempts to re-declare 'obj_p'
0,Foo (obj_p) ; // Ok - Comma operator
Foo ((0,obj_p)) ; // Ok - Comma operator
Foo (Obj_P(obj_p)) ; // Ok - Explicit type case
return 0 ;
}
[ Code Ends ]----------------------------------------------
[ Compile Info Starts ]------------------------------------
Compiled with: gcc -v -save-temps main.cpp
Reading specs from /usr/lib/gcc/i686-pc-cygwin/3.4.4/specs
Configured with: /usr/build/package/orig/test.respin/gcc-3.4.4-3/configure
--verbose --prefix=/usr --exec-prefix=/usr --sysconfdir=/etc --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--enable-languages=c,ada,c++,d,f77,pascal,java,objc --enable-nls
--without-included-gettext --enable-version-specific-runtime-libs --without-x
--enable-libgcj --disable-java-awt --with-system-zlib --enable-interpreter
--disable-libgcj-debug --enable-threads=posix --enable-java-gc=boehm
--disable-win32-registry --enable-sjlj-exceptions --enable-hash-synchronization
--enable-libstdcxx-debug
Thread model: posix
gcc version 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)
/usr/lib/gcc/i686-pc-cygwin/3.4.4/cc1plus.exe -E -quiet -v -D__CYGWIN32__
-D__CYGWIN__ -Dunix -D__unix__ -D__unix -idirafter
/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../include/w32api -idirafter
/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686-pc-cygwin/lib/../../include/w32api
main.cpp -mtune=pentiumpro -o main.ii
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory
"/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686-pc-cygwin/include"
ignoring duplicate directory
"/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686-pc-cygwin/lib/../../include/w32api"
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/i686-pc-cygwin
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/backward
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include
/usr/include
/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../include/w32api
End of search list.
/usr/lib/gcc/i686-pc-cygwin/3.4.4/cc1plus.exe -fpreprocessed main.ii -quiet
-dumpbase main.cpp -mtune=pentiumpro -auxbase main -version -o main.s
GNU C++ version 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)
(i686-pc-cygwin)
compiled by GNU C version 3.4.4 (cygming special, gdc 0.12, using dmd
0.125).
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
main.cpp: In function `int main()':
main.cpp:28: error: conflicting declaration 'Foo obj_p'
main.cpp:26: error: 'obj_p' has a previous declaration as `Obj*obj_p'
main.cpp:28: error: declaration of `Foo obj_p'
main.cpp:26: error: conflicts with previous declaration `Obj*obj_p'
main.cpp:28: error: no matching function for call to `Foo::Foo()'
main.cpp:10: note: candidates are: Foo::Foo(const Foo&)
main.cpp:13: note: Foo::Foo(Obj*)
[ Compile Info Ends ]-----------------------------------------
[ Preprocessed Output Begins ]--------------------------------
# 1 "main.cpp"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "main.cpp"
struct Obj
{
int a ;
} ;
typedef Obj * Obj_P ;
class Foo
{
public :
inline Foo (Obj_P obj_p) : obj_p (obj_p)
{
}
private :
Obj_P obj_p ;
} ;
int main (void)
{
Obj_P obj_p = 0 ;
Foo (obj_p) ;
0,Foo (obj_p) ;
Foo ((0,obj_p)) ;
Foo (Obj_P(obj_p)) ;
return 0 ;
}
[ Preprocessed Output Ends ]--------------------------------
--
Summary: Temporary object incorrectly parsed as confilcint
declaration
Product: gcc
Version: 3.4.4
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: danq at acacetus dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31328
