c++/6048: CPLUS_INCLUDE_PATH confused by semicolons

[Christoph Bugel <cbugel at netvision dot net dot il>]

>Number:         6048
>Category:       c++
>Synopsis:       CPLUS_INCLUDE_PATH confused by semicolons
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Mar 23 05:46:01 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     Christoph Bugel <cbugel@netvision.net.il>
>Release:        gcc 3.0.4
>Organization:
>Environment:
i686-pc-linux-gnu
>Description:
I have a weird case where a file called 'new',
accidentally left in my current directory, would confuse
g++: #include <string> would load my local 'new' instead
of looking in the system directories first.
This is very confusing to a nonsuspecting user.

Eventually I noticed that CPLUS_INCLUDE_PATH gets
defined in /etc/profile.d/qt.sh. After reading PR 5997,
I suspect that using CPATH would have been a more
sensible choice (should I report this to QT?), but it
still looks like a g++ bug to me:

Most interestingly, I noticed that the bug triggers only
when the path ends with a semicolon:

CPLUS_INCLUDE_PATH=/usr/lib/qt/include   = OK
CPLUS_INCLUDE_PATH=/usr/lib/qt/include:  = BUG

In the second case the '.' directory is added to the
searchpath, as evident from the g++ -v output below.


$ export CPLUS_INCLUDE_PATH=/usr/lib/qt/include: && g++ -v hw.cc

Reading specs from /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4/specs
Configured with: ../gcc-3.0.4/configure --prefix=/usr/local --enable-threads --enable-languages=c++,java
Thread model: posix
gcc version 3.0.4
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4/cc1plus -v -D__GNUC__=3 -D__GNUC_MINOR__=0 -D__GNUC_PATCHLEVEL__=4 -D__ELF__ -Dunix -Dlinux -D__ELF__ -D__unix__ -D__linux__ -D__unix -D__linux -Asystem=posix -D__NO_INLINE__ -D__STDC_HOSTED__=1 -D_GNU_SOURCE -Acpu=i386 -Amachine=i386 -Di386 -D__i386 -D__i386__ -D__tune_i686__ -D__tune_pentiumpro__ hw.cc -D__GNUG__=3 -D__GXX_DEPRECATED -D__EXCEPTIONS -D__GXX_ABI_VERSION=100 -quiet -dumpbase hw.cc -version -o /tmp/ccnJDaiN.s
GNU CPP version 3.0.4 (cpplib) (i386 Linux/ELF)
GNU C++ version 3.0.4 (i686-pc-linux-gnu)
        compiled by GNU C version 3.0.4.
ignoring nonexistent directory "/usr/local/i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/qt/include
 .
 /usr/local/include/g++-v3
 /usr/local/include/g++-v3/i686-pc-linux-gnu
 /usr/local/include/g++-v3/backward
 /usr/local/include
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4/include
 /usr/include
End of search list.
<internal>: In static member function `static std::basic_string<_CharT,
   _Traits, _Alloc>::_Rep* std::basic_string<_CharT, _Traits,
   _Alloc>::_Rep::_S_create(unsigned int, const _Alloc&) [with _CharT = char,
   _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]':
/usr/local/include/g++-v3/bits/basic_string.tcc:392:   instantiated from `_CharT* std::basic_string<_CharT, _Traits, _Alloc>::_Rep::_M_clone(const _Alloc&, typename _Alloc::size_type) [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>]'


For comparison: without semicolon it works fine:
$ export CPLUS_INCLUDE_PATH=/usr/lib/qt/include && g++ -v hw.cc

Reading specs from /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4/specs
Configured with: ../gcc-3.0.4/configure --prefix=/usr/local --enable-threads --enable-languages=c++,java
Thread model: posix
gcc version 3.0.4
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4/cc1plus -v -D__GNUC__=3 -D__GNUC_MINOR__=0 -D__GNUC_PATCHLEVEL__=4 -D__ELF__ -Dunix -Dlinux -D__ELF__ -D__unix__ -D__linux__ -D__unix -D__linux -Asystem=posix -D__NO_INLINE__ -D__STDC_HOSTED__=1 -D_GNU_SOURCE -Acpu=i386 -Amachine=i386 -Di386 -D__i386 -D__i386__ -D__tune_i686__ -D__tune_pentiumpro__ hw.cc -D__GNUG__=3 -D__GXX_DEPRECATED -D__EXCEPTIONS -D__GXX_ABI_VERSION=100 -quiet -dumpbase hw.cc -version -o /tmp/ccoFItg7.s
GNU CPP version 3.0.4 (cpplib) (i386 Linux/ELF)
GNU C++ version 3.0.4 (i686-pc-linux-gnu)
        compiled by GNU C version 3.0.4.
ignoring nonexistent directory "/usr/local/i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/qt/include
 /usr/local/include/g++-v3
 /usr/local/include/g++-v3/i686-pc-linux-gnu
 /usr/local/include/g++-v3/backward
 /usr/local/include
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4/include
 /usr/include
End of search list.
 as -V -Qy -o /tmp/ccBFKG8H.o /tmp/ccoFItg7.s
GNU assembler version 2.11.90.0.19 (i386-slackware-linux) using BFD version 2.11.90.0.19
 /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4/collect2 -m elf_i386 -dynamic-linker /lib/ld-linux.so.2 /usr/lib/crt1.o /usr/lib/crti.o /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4/crtbegin.o -L/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4 -L/usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4/../../.. /tmp/ccBFKG8H.o -lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc /usr/local/lib/gcc-lib/i686-pc-linux-gnu/3.0.4/crtend.o /usr/lib/crtn.o
>How-To-Repeat:
$ hw.cc:
-------------------------------
#include <string>
#include <iostream>
int main()
{
        std::string a = "hello";
        std::cout << a << std::endl;
        return 0;
}
-------------------------------
$ touch new
$ export CPLUS_INCLUDE_PATH=/usr/lib/qt/include: && g++ -v hw.cc
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: