Desabilitando o C ++ 11 no GCC 7.3

11

Parece que no Ubuntu 18.04, o g ++ padrão fornecido (versão 7.3.0) é executado no modo compatível com C ++ 11 por padrão. Estou recebendo alguns erros nos meus códigos antigos que não são compatíveis com C ++ 11. Eu instalei o g ++ - 6 (versão 6.4.0) e os programas estão sendo compilados corretamente. É possível desativar o modo C ++ 11 em g ++ - 7?

gcc c++ g++ Soo
fonte
2
Na verdade, o modo padrão do GCC 6 já é C ++ 14 . O GCC 7 adiciona suporte ao C ++ 17; provavelmente é suficiente apenas desativar esse material do C ++ 17. Não há necessidade de voltar ao C ++ 11. Voltando para C ++ 98 é realmente um exagero enorme (underkill?)
MSalters
5
o que você fez em programas antigos que não são compatíveis? Você pode ter conseguido fazer coisas que não lhe eram permitidas devido a erros. Nesse caso, você não ganhará nada ao ir para o c ++ 98.
whn
9
@snb: Ou eles usaram std::auto_ptr, ou usado autoem seu disfarce original, ou eles têm conversões estreitamento agora ilegais, ou que eles usaram export, ou, ou, ou
Leveza raças em Orbit
1
@snb: stackoverflow.com/a/6402166/560648
Lightness Races in Orbit
2
@LightnessRacesinOrbit A maior parte disso teria sido uma prática ruim antes do C ++ 11.
whn

Respostas:

20

Tente adicionar -std=gnu++98, provavelmente era o padrão para o gcc 6.4.0.

Exemplo:

g++ -std=gnu++98 hello.cpp -o hello
pim
fonte
5
Se você precisar de compatibilidade ABI com código compilado por GCCs velhos, você vai querer -D_GLIBCXX_USE_CXX11_ABI=0bem
Tavian Barnes
2
Ou -std=gnu++03para o último padrão anterior ao C ++ 11. Também vale mencionar que -std=c++03desativará algumas extensões GNU que são incompatíveis com o estrito ISO C ++.
Peter Cordes
1
No Godbolt compiler explorer, C ++ 14 é o padrão para g ++ 6.3 godbolt.org/g/x2xPCS . C ++ 98 era o padrão para o g ++ 5.5 e mais antigo. Eu verifiquei o valor de __cplusplus: Como determinar a versão do padrão C ++ usado pelo compilador?
Peter Cordes
1

No man g++você pode selecionar entre diferentes dialetos: 

Options Controlling C Dialect
   The following options control the dialect of C (or languages derived
   from C, such as C++, Objective-C and Objective-C++) that the compiler
   accepts:

  -ansi
       In C mode, this is equivalent to -std=c90. In C++ mode, it is
       equivalent to -std=c++98.

       This turns off certain features of GCC that are incompatible with
       ISO C90 (when compiling C code), or of standard C++ (when compiling
       C++ code), such as the "asm" and "typeof" keywords, and predefined
       macros such as "unix" and "vax" that identify the type of system
       you are using.  It also enables the undesirable and rarely used ISO
       trigraph feature.  For the C compiler, it disables recognition of
       C++ style // comments as well as the "inline" keyword.

  -std=
       Determine the language standard.   This option is currently only
       supported when compiling C or C++.

       The compiler can accept several base standards, such as c90 or
       c++98, and GNU dialects of those standards, such as gnu90 or
       gnu++98.  When a base standard is specified, the compiler accepts
       all programs following that standard plus those using GNU
       extensions that do not contradict it.  For example, -std=c90 turns
       off certain features of GCC that are incompatible with ISO C90,
       such as the "asm" and "typeof" keywords, but not other GNU
       extensions that do not have a meaning in ISO C90, such as omitting
       the middle term of a "?:" expression. On the other hand, when a GNU
       dialect of a standard is specified, all features supported by the
       compiler are enabled, even when those features change the meaning
       of the base standard.  As a result, some strict-conforming programs
       may be rejected.  The particular standard is used by -Wpedantic to
       identify which features are GNU extensions given that version of
       the standard. For example -std=gnu90 -Wpedantic warns about C++
       style // comments, while -std=gnu99 -Wpedantic does not.

       A value for this option must be provided; possible values are

       c90
       c89
       iso9899:1990
           Support all ISO C90 programs (certain GNU extensions that
           conflict with ISO C90 are disabled). Same as -ansi for C code.

       iso9899:199409
           ISO C90 as modified in amendment 1.

       c99
       c9x
       iso9899:1999
       iso9899:199x
           ISO C99.  This standard is substantially completely supported,
           modulo bugs and floating-point issues (mainly but not entirely
           relating to optional C99 features from Annexes F and G).  See
           <http://gcc.gnu.org/c99status.html> for more information.  The
           names c9x and iso9899:199x are deprecated.

       c11
       c1x
       iso9899:2011
           ISO C11, the 2011 revision of the ISO C standard.  This
           standard is substantially completely supported, modulo bugs,
           floating-point issues (mainly but not entirely relating to
           optional C11 features from Annexes F and G) and the optional
           Annexes K (Bounds-checking interfaces) and L (Analyzability).
           The name c1x is deprecated.

       gnu90
       gnu89
           GNU dialect of ISO C90 (including some C99 features).

       gnu99
       gnu9x
           GNU dialect of ISO C99.  The name gnu9x is deprecated.

       gnu11
       gnu1x
           GNU dialect of ISO C11.  This is the default for C code.  The
           name gnu1x is deprecated.

       c++98
       c++03
           The 1998 ISO C++ standard plus the 2003 technical corrigendum
           and some additional defect reports. Same as -ansi for C++ code.
       gnu++98
       gnu++03
           GNU dialect of -std=c++98.

       c++11
       c++0x
           The 2011 ISO C++ standard plus amendments.  The name c++0x is
           deprecated.

       gnu++11
       gnu++0x
           GNU dialect of -std=c++11.  The name gnu++0x is deprecated.

       c++14
       c++1y
           The 2014 ISO C++ standard plus amendments.  The name c++1y is
           deprecated.

       gnu++14
       gnu++1y
           GNU dialect of -std=c++14.  This is the default for C++ code.
           The name gnu++1y is deprecated.

       c++1z
           The next revision of the ISO C++ standard, tentatively planned
           for 2017.  Support is highly experimental, and will almost
           certainly change in incompatible ways in future releases.

       gnu++1z
           GNU dialect of -std=c++1z.  Support is highly experimental, and
           will almost certainly change in incompatible ways in future
           releases.
abu_bua
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