Hi all, I'm trying to figure out how to get gcc to warn on a specific problem that we found in our source code. I've attached a simple test program that has a few places where floating point precision can potentially be lost or cause problems. Specifically: 1) Line 12, returns a double as a float without an explicit cast - loss of precision. Would like a warning here. 2) Line 19, same problem, but with fixed point - returns an int as a short, without a cast - loss of precision, would like a warning 3) Line 31, subtracts a float from a double (the constant is treated as a double, the variable is explicitly cast as a float. In this particular case, as can be seen in the printf on line 34, pi/2 - pi/2 does not equal zero. This seems like it might be harder to check for, but I'd love to see a warning here as well. Note that the method on line 15, where I return a double as an int does have a warning, even without any -W... options: tryFloat.C: In member function `int Test::getDI() const': tryFloat.C:15: warning: return to `int' from `const double' tryFloat.C:15: warning: argument to `int' from `const double' The man page on gcc 3.4 and above seem to imply that -Wextra should have checks for these floating point precision problems - however I've tried gcc 3.3.2, 3.4.x, 4.0.0, and 4.1.1, and no matter how many -W options I add, -pedantic, -ansi, etc, to make the compile as strict as possible, I can't get warnings for these floating point problems. Can anyone point out how to get warnings, or explain why these aren't candidates for a warning? Finally, and probably unrelated, when I used gcc 4.0.0 and 4.1.1, on RedHat Enterprise 4 (ES), the warnings I do get are formatted badly - ie, the warning above (from 3.3.2) shows up as: tryFloat.C: In member function â: tryFloat.C:15: warning: converting to â from â I don't know what the â character is, but thats clearly not very useful. The gcc 4.1.1 is a freshly compiled install - I compiled it with RedHat's gcc 3.4.5 using: Configured with: /usr/src/gcc-4.1.1/configure --prefix=/usr/local/gcc-4.1.1 --disable-shared --enable-threads=posix --enable-lang=c,c++ and make bootstrap. Any ideas on this one? Thanks very much, Scott Lipcon
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