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

From: Antonio Diaz Diaz
Subject: Re: [Bug-ddrescue] Cannot compile with uClibc-ng
Date: Sun, 12 May 2019 12:48:37 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i586; en-US; rv: Gecko/20110420 SeaMonkey/2.0.14

Hi Rosen,

Rosen Penev wrote:
Build log of the issue:

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 (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,

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