In fact both gcc and tcc are correct because your snippet uses an undefined behavior.
"a"=="a" compares the address of two strings which are the address of the first character, not the character itself as you said. Now, which one is correct? None or both. A litteral string is supposed to be constant as if declared: const char *s="a"; Because litteral strings are constant, a compiler is allowed to share different strings and define only one instance. Gcc shares common strings and this "a"=="a" compares the addresses of the same object. It returns 1. Tcc, which is also allowed, makes two copies and addresses are different. Expression returns 0. C. -----Original Message----- From: tinycc-devel-bounces+eligis=orange...@nongnu.org [mailto:tinycc-devel-bounces+eligis=orange...@nongnu.org] On Behalf Of Henry Kroll Sent: lundi 8 novembre 2010 12:36 To: tinycc-devel@nongnu.org Subject: [Tinycc-devel] compare quoted strings This little snippet prints "true" if compiled with gcc and "not true" if compiled with tcc. int main (void){ printf ("%sok\n","a"=="a"?"":"not "); return 0; } Note that "a"=="a" is not what it looks like. We are comparing the address of the pointer "a" with itself. If the book I just looked at (Banahan, et al., 1991) interprets the standard correctly, a quoted string serves as a pointer to the first element, thus "a"=="a" should return true. Ref Banahan, Mike, Brady, Declan and Doran, Mark. (1991). The C Book - Character handling. Chapter 5.4. Retrieved November 8, 2010, from http://publications.gbdirect.co.uk/c_book/chapter5/character_handling.html _______________________________________________ Tinycc-devel mailing list Tinycc-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/tinycc-devel ---------------------------------------------------------------------------- ----------- Orange vous informe que cet e-mail a ete controle par l'anti-virus mail. Aucun virus connu a ce jour par nos services n'a ete detecte. _______________________________________________ Tinycc-devel mailing list Tinycc-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/tinycc-devel
