Thread: Shouldn't this give a warning?

  1. 03-25-2015 #1
    homer_3
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    Shouldn't this give a warning?

    I always forget which one has stricter rules (C or C++) but shouldn't this give a warning in at least one of the languages?

    Code:
    int x = 120000;
short y = x;
    I've tried compiling with both c and c++ using

    Code:
    g++ -c -Wall test.cpp
gcc -c -Wall test.cpp
    Neither give a warning.
  2. 03-25-2015 #2
    jimblumberg
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    What warning are you expecting?

    Why?

    Jim
  3. 03-25-2015 #3
    Elysia
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    Warnings are compiler-specific. The language does not mandate what warnings should emitted. Nevertheless, some compilers (e.g. Visual Studio) does provide warnings for this sort of code:

    Code:
    int main()
{
	int x = 0;
	float y = x;
	int z = y;
}
    Warning C4244 'initializing': conversion from 'float' to 'int', possible loss of data
    Warning C4244 'initializing': conversion from 'int' to 'float', possible loss of data
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.
  4. 03-25-2015 #4
    manasij7479
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    Use the "-Wconversion" flag.
    Why it does not get enabled with -Wall, I have no idea.
  5. 03-25-2015 #5
    homer_3
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    Quote Originally Posted by manasij7479 View Post
    Use the "-Wconversion" flag.
    Why it does not get enabled with -Wall, I have no idea.

    Thanks. Found this write up on that flag. https://gcc.gnu.org/wiki/NewWconversion. Unfortunately, my compiler is 4.1 so it seems like I may not have this option.
  6. 03-25-2015 #6
    laserlight
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    Quote Originally Posted by manasij7479 View Post
    Use the "-Wconversion" flag.
    Why it does not get enabled with -Wall, I have no idea.

    Interestingly, even -Wextra does not include -Wconversion
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way
  7. 03-25-2015 #7
    Elysia
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    Quote Originally Posted by homer_3 View Post
    Thanks. Found this write up on that flag. https://gcc.gnu.org/wiki/NewWconversion. Unfortunately, my compiler is 4.1 so it seems like I may not have this option.
    That compiler version is very outdated. Highly recommend upgrading some way or another.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.
  8. 03-25-2015 #8
    cyberfish
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    Quote Originally Posted by homer_3 View Post
    Thanks. Found this write up on that flag. https://gcc.gnu.org/wiki/NewWconversion. Unfortunately, my compiler is 4.1 so it seems like I may not have this option.
    :S why are you using an 8-years-old compiler?!

    GCC is open source. You can upgrade for free!
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