• Undefined Reference To Ceil
• Undefined Reference To Ceiling
• Ceilf
• Perl Ceil
• Undefined Reference To Symbol 'ceil@@glibc_2.0'

Example

The function I tried to use was ceil and I get the following error:: undefined reference to `ceil' collect2: ld returned 1 exit status I am using the latest Ubuntu and math.h is there. I tried to use -lm in a different computer and it work perfectly. Does anyone know how to solve this problem?

Undefined Reference To Ceil

• That guide is a copy of the one from here & also doesn't reflect some changes that were recently made. The changes came from discussions we had about installing static libs & includes to /usr/local & the potential issues that doing so may cause.
• Undefined references can have different reasons. Here are some: 1) The most common issue is about the the inline behavior. Clang is following by default the C99 standard while gcc promote GNU89. The following code will build with gcc but fails with.

One of the most common errors in compilation happens during the linking stage. The error looks similar to this:

Undefined Reference To Ceiling

Because ceil is a static method of Math, you always use it as Math.ceil, rather than as a method of a Math object you created (Math is not a constructor). Double ceil (double x); float ceil (float x); long double ceil (long double x); Round up value Rounds x upward, returning the smallest integral value that is not less than x.

So let's look at the code that generated this error:

We see here a declaration of foo (int foo();) but no definition of it (actual function). So we provided the compiler with the function header, but there was no such function defined anywhere, so the compilation stage passes but the linker exits with an Undefined reference error.
To fix this error in our small program we would only have to add a definition for foo:

Now this code will compile. An alternative situation arises where the source for foo() is in a separate source file foo.c (and there's a header foo.h to declare foo() that is included in both foo.c and undefined_reference.c). Then the fix is to link both the object file from foo.c and undefined_reference.c, or to compile both the source files:

Ceilf

Or:

A more complex case is where libraries are involved, like in the code:

The code is syntactically correct, declaration for pow() exists from #include <math.h>, so we try to compile and link but get an error like this:

Perl Ceil

This happens because the definition for pow() wasn't found during the linking stage. To fix this we have to specify we want to link against the math library called libm by specifying the -lm flag. (Note that there are platforms such as macOS where -lm is not needed, but when you get the undefined reference, the library is needed.)

So we run the compilation stage again, this time specifying the library (after the source or object files):

Undefined Reference To Symbol 'ceil@@glibc_2.0'

And it works!

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