c++/3747: ambiguity between `T operator[](unsigned)` and `T* operator`

[jan at etpmod dot phys dot tue dot nl]

>Number:         3747
>Category:       c++
>Synopsis:       ambiguity between `T operator[](unsigned)` and `T* operator`
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          rejects-legal
>Submitter-Id:   net
>Arrival-Date:   Fri Jul 20 08:16:03 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator:     jan@etpmod.phys.tue.nl
>Release:        gcc version 3.0
>Organization:
>Environment:
Linux 2.4.6,
Configured with: ../../src/egcs-3.0/configure --enable-version-specific-runtime-libs --prefix=/usr/local/egcs-3.0
>Description:
The attached code (file strtest.cpp) fails to compile with egcs version 3.0 (or with the head branch). This is a regression wrt 2.95.x

Gcc-3.0:pcjan:/home/jan/src>g++ -c strtest.cpp
strtest.cpp:6: choosing `char& A::operator[](unsigned int)' over `operator[]'
strtest.cpp:6:   because worst conversion for the former is better than worst
   conversion for the latter

The compiler is in doubt: it cannot choose between A.operator[](0) and 
A.(operator const char*).`c-builtin[]`(0). IMHO the first conversion has preference and should be chosen. 
>How-To-Repeat:
Compile the attached file strtest.cpp
>Fix:
This bug breaks existing code, I could not think of a transparent workaround. If `0' is replaced with `0u' (unsigned 0), the snippet compiles properly.
>Release-Note:
>Audit-Trail:
>Unformatted:
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