2010/10/12 Ian Lance Taylor <iant@xxxxxxxxxx>: > Jens Rehsack <rehsack@xxxxxxxxxxxxxx> writes: > >> 2010/10/12 Ian Lance Taylor <iant@xxxxxxxxxx>: >>> Jens Rehsack <rehsack@xxxxxxxxxxxxxx> writes: >>> >>>> I currently write some c++ code using libConfuse >>>> (http://savannah.nongnu.org/projects/confuse/). >>>> During initialisation of the required cfg_opt_t structures I get a >>>> (very) lot of warnings like: >>>> c2.cpp:11: warning: deprecated conversion from string constant to ‘char*' >>>> >>>> I attached a small example to demonstrate the problem. It's not >>>> trivial - changing the "name" member >>>> of struct demo being const, free failes (and is invalid, because >>>> there're demo_opt instances with >>>> modifyable names). >>>> >>>> Any suggestions welcome. >>>> 1) Killing the warning with -Wno-... is not an option >>>> 2) Remove the finding using const_cast<char *>() is the same as (1) >>>> 3) initializing the struct using strdup is neither reasonable >>> >>> I'm not sure what you want us to suggest. You say that the names are >>> modifiable. >> >> Where do I say that? I apologize saying this (must be happened because >> of my not so good english). > > "changing the "name" member of struct demo being const, free failes (and > is invalid, because there're demo_opt instances with modifyable names)." > > I apologize if I misread that sentence. I tried to say (and you can easily verify by modify the attached example of the original post): when I modify the structure to have "const char *name" members like: struct demo_opt { const char *name; int flags; }; c1.c: demo_free() fails in line 52. >>> String constants are not modifiable. If the strings are >>> indeed modified, and you pass in a string constant, then your program is >>> going to crash when the library tries to modify the strings. The gcc >>> warning is helpfully pointing that out. >> >> Correct. And if the strings are not modifiable? (I thought I provided an >> example which shows, that they neither are assumed being modifiable >> nor being modified). >> >>> This is not a gcc issue. It's a C++ language issue. If you need a >>> modifiable string, then you must not use a string constant. >> >> How can this being expressed without declaring dozen of helper >> variables? > > I am not sure that I understand what you are asking. Can you provide a > short, standalone, bit of code showing the problem? Attached at the first mail :) Or is it to long? > Is there any reason to think that this is a gcc issue rather than a C++ > issue? I don't know. I encounter this problem first time - and I don't have another c++ compiler to test if they deal better. It's likely a c++ language issue, but I can't imagine that there is no way out (or better I hope that there is a way to deal with such situations). /Jens
