re PR c/7776 (const char* p = "foo"; if (p == "foo") ... is compiled without warning!)
PR c/7776
* common.opt (Wstring-literal-comparison): New command line option.
* c-opts.c (c_common_handle_option): Set it with -Wall.
* c-typeck.c (parser_build_binary_op): Issue warning if either
operand of a comparison operator is a string literal, except for
testing equality or inequality against NULL.
* doc/invoke.texi: Document new -Wstring-literal-comparison option.
* gcc.dg/Wstring-literal-comparison-1.c: New test case.
* gcc.dg/Wstring-literal-comparison-2.c: Likewise.
* gcc.dg/Wstring-literal-comparison-3.c: Likewise.
* gcc.dg/Wstring-literal-comparison-4.c: Likewise.
From-SVN: r108018