Re: [Bug-ddrescue] Cannot compile with uClibc-ng

[Rosen Penev]

On Sun, May 12, 2019 at 3:48 AM Antonio Diaz Diaz <address@hidden> wrote:
>
> Hi Rosen,
>
> Rosen Penev wrote:
> > Build log of the issue:
> > https://downloads.openwrt.org/snapshots/faillogs/arc_arc700/packages/gddrescue/compile.txt
> >
> > I've tried including extra headers but it doesn't work. Only thing
> > that works is to use the plain variants of fgetc, feof, and ferror.
> >
> >> From looking at the uClibc-ng source code, I can't find a good reason
> > why this is not working. Interestingly enough, the other ones like
> > std::fopen work.
>
> It seems that uClibc-ng is defining fgetc, fputc, feof, and ferror as
> macros and not including them in std.
>
>  From the C++ 2003 standard:
>
> "Except as noted in clauses 18 through 27, the contents of each header
> cname shall be the same as that of the corresponding header name.h, as
> specified in ISO/IEC 9899:1990 Programming Languages C (Clause 7), or
> ISO/IEC:1990 Programming Languages--C AMENDMENT 1: C Integrity, (Clause
> 7), as appropriate, as if by inclusion. In the C++ Standard Library,
> however, the declarations and definitions (except for names which are
> defined as macros in C) are within namespace scope (3.3.5) of the
> namespace std."
>
> But these four functions do not seem to be defined as macros in C.
>
> IMO this is a bug in uClibc-ng
Even so, it might still make sense to work around it.

For now, I've disabled building gddrescue with uClibc-ng in OpenWrt.
> (maybe caused by lack of clarity in the
> C++ standard), because even the C functions that are alowed to be
> defined as macros (putc, getc) should be included in std for
> consistency. Just imagine the chaos if std::getc were defined or
> undefined depending on how it is implemented.
>
>  From the C 1999 standard:
>
> "The getc function is equivalent to fgetc, except that if it is
> implemented as a macro, it may evaluate stream more than once, so the
> argument should never be an expression with side effects."
>
> Note that getc is allowed, not required, to be implemented as a macro.
>
>
> Best regards,
> Antonio.