Clang vs GCC per il mio progetto di sviluppo Linux

Clang vs GCC per il mio progetto di sviluppo Linux

Sono al college e per un progetto stiamo usando C. Abbiamo esplorato GCC e Clang e Clang sembra essere molto più intuitivo di GCC. Di conseguenza, mi chiedo quali siano i vantaggi o gli svantaggi dell'utilizzo del clang, al contrario di GCC, per lo sviluppo in C e C++ su Linux?

Nel mio caso questo verrebbe utilizzato per i programmi a livello di studenti, non per la produzione.

Se uso Clang, devo eseguire il debug con GDB e utilizzare GNU Make, o utilizzare un altro debugger e make utility?

Risposte:

MODIFICA:

I ragazzi di gcc hanno davvero migliorato l'esperienza di diagnosi in gcc (ah competition). Hanno creato una pagina wiki per mostrarlo qui. gcc 4.8 ora ha anche una diagnostica abbastanza buona (gcc 4.9x ha aggiunto il supporto del colore). Clang è ancora in testa, ma il gap si sta riducendo.

Originale:

Per gli studenti, consiglierei incondizionatamente Clang.

Le prestazioni in termini di codice generato tra gcc e Clang ora non sono chiare (anche se penso che gcc 4.7 sia ancora in vantaggio, non ho ancora visto benchmark conclusivi), ma per gli studenti non importa comunque.

D'altra parte, la diagnostica estremamente chiara di Clang è decisamente più facile da interpretare per i principianti.

Considera questo semplice snippet:

#include <string>
 #include <iostream>
 struct Student {
 std::string surname;
 std::string givenname;
 }
 std::ostream& operator<<(std::ostream& out, Student const& s) {
   return out << "{" << s.surname << ", " << s.givenname << "}";
 }
 int main() {
   Student me = { "Doe", "John" };
   std::cout << me << "\n";
 }

Noterai subito che manca il punto e virgola dopo la definizione del Student classe, giusto :)?

Ebbene, anche gcc se ne accorge, in un certo senso:

prog.cpp:9: error: expected initializer before ‘&’ token
 prog.cpp: In function ‘int main()’:
 prog.cpp:15: error: no match for ‘operator<<’ in ‘std::cout << me’
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:112: note: candidates are: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>& (*)(std::basic_ostream<_CharT, _Traits>&)) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:121: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ios<_CharT, _Traits>& (*)(std::basic_ios<_CharT, _Traits>&)) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:131: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::ios_base& (*)(std::ios_base&)) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:169: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:173: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:177: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/bits/ostream.tcc:97: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:184: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/bits/ostream.tcc:111: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:195: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:204: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:208: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:213: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:217: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(float) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:225: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(long double) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:229: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(const void*) [with _CharT = char, _Traits = std::char_traits<char>]
 /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/bits/ostream.tcc:125: note:                 std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_streambuf<_CharT, _Traits>*) [with _CharT = char, _Traits = std::char_traits<char>]

E anche Clang non è esattamente protagonista qui, ma comunque:

/tmp/webcompile/_25327_1.cc:9:6: error: redefinition of 'ostream' as different kind of symbol
 std::ostream& operator<<(std::ostream& out, Student const& s) {
      ^
 In file included from /tmp/webcompile/_25327_1.cc:1:
 In file included from /usr/include/c++/4.3/string:49:
 In file included from /usr/include/c++/4.3/bits/localefwd.h:47:
 /usr/include/c++/4.3/iosfwd:134:33: note: previous definition is here
   typedef basic_ostream<char>           ostream;        ///< @isiosfwd
                                         ^
 /tmp/webcompile/_25327_1.cc:9:13: error: expected ';' after top level declarator
 std::ostream& operator<<(std::ostream& out, Student const& s) {
             ^
             ;
 2 errors generated.

Scelgo di proposito un esempio che attiva un messaggio di errore poco chiaro (proveniente da un'ambiguità nella grammatica) piuttosto che i tipici esempi "Oh mio dio Clang leggi la mia mente". Tuttavia, notiamo che Clang evita la marea di errori. Non c'è bisogno di spaventare gli studenti.

Alcune risposte al codice

#include <string>
#include <iostream>
 struct Student { std::string surname;
std::string givenname;
}  std::ostream&
operator<<(std::ostream&
out, Student const&
s) {   return out <<
"{" <<
s.surname <<
", " <<
s.givenname <<
"}";
}  int main() {   Student me = { "Doe", "John" };
  std::cout <<
me <<
"\n";
}

prog.cpp:9: error: expected initializer before ‘&’ token prog.cpp: In function ‘int main()’: prog.cpp:15: error: no match for ‘operator<<’ in ‘std::cout <<
me’ /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:112: note: candidates are: std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>&
(*)(std::basic_ostream<_CharT, _Traits>&)) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:121: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ios<_CharT, _Traits>&
(*)(std::basic_ios<_CharT, _Traits>&)) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:131: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(std::ios_base&
(*)(std::ios_base&)) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:169: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:173: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:177: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/bits/ostream.tcc:97: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:184: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/bits/ostream.tcc:111: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:195: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:204: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:208: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:213: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:217: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(float) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:225: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(long double) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/ostream:229: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(const void*) [with _CharT = char, _Traits = std::char_traits<char>] /usr/lib/gcc/i686-pc-linux-gnu/4.3.4/include/g++-v4/bits/ostream.tcc:125: note:
std::basic_ostream<_CharT, _Traits>&
std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_streambuf<_CharT, _Traits>*) [with _CharT = char, _Traits = std::char_traits<char>]

/tmp/webcompile/_25327_1.cc:9:6: error: redefinition of 'ostream' as different kind of symbol std::ostream&
operator<<(std::ostream&
out, Student const&
s) {
^ In file included from /tmp/webcompile/_25327_1.cc:1: In file included from /usr/include/c++/4.3/string:49: In file included from /usr/include/c++/4.3/bits/localefwd.h:47: /usr/include/c++/4.3/iosfwd:134:33: note: previous definition is here   typedef basic_ostream<char>
    ostream;
 ///<
@isiosfwd
^ /tmp/webcompile/_25327_1.cc:9:13: error: expected ';' after top level declarator std::ostream&
operator<<(std::ostream&
out, Student const&
s) { ^ ;
2 errors generated.

main() {
puts("Hello, world!");
}