https://bugzilla.kernel.org/show_bug.cgi?id=60749 --- Comment #4 from Michael Kerrisk <mtk.manpages@xxxxxxxxx> --- Walter Harms pointed out on linux-man that what is going on here is that gcc implements some functions (many of them are math functions) as built-ins. There is a list here: http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html When the function is a compiled as a gcc built-in, then it is not necessary link against the corresponding library. However, I'm unwilling to add that level of detail about a specific compiler to the various manual pages. On Thu, Aug 15, 2013 at 10:36 PM, <bugzilla-daemon@xxxxxxxxxxxxxxxxxxx> wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=60749 > > Bug ID: 60749 > Summary: Do not need to link against -lm for fabs*() > Product: Documentation > Version: unspecified > Hardware: All > OS: Linux > Status: NEW > Severity: low > Priority: P1 > Component: man-pages > Assignee: documentation_man-pages@xxxxxxxxxxxxxxxxxxxx > Reporter: orion@xxxxxxxxxxxxx > Regression: No > > From the fabs(3) man page: > > SYNOPSIS > #include <math.h> > > double fabs(double x); > float fabsf(float x); > long double fabsl(long double x); > > Link with -lm. > > > At least on RHEL5+ one does not appear to need to link with -lm. > > # cat fabs.c > #include <math.h> > #include <stdlib.h> > #include <stdio.h> > > int main(int argc, char **argv) > { > printf("%f\n",fabs(atof(argv[1]))); > printf("%f\n",fabsf((float)atof(argv[1]))); > printf("%Lf\n",fabsl((long double)atof(argv[1]))); > return 0; > } > # gcc -g -Wall fabs.c > # ./a.out -2.5 > 2.500000 > 2.500000 > 2.500000 > # gcc -v > Using built-in specs. > Target: x86_64-redhat-linux > Configured with: ../configure --prefix=/usr --mandir=/usr/share/man > --infodir=/usr/share/info --enable-shared --enable-threads=posix > --enable-checking=release --with-system-zlib --enable-__cxa_atexit > --disable-libunwind-exceptions --enable-libgcj-multifile > --enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk > --disable-dssi --disable-plugin > --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre --with-cpu=generic > --host=x86_64-redhat-linux > Thread model: posix > gcc version 4.1.2 20080704 (Red Hat 4.1.2-54) > > -- > You are receiving this mail because: > You are watching the assignee of the bug. -- You are receiving this mail because: You are watching the assignee of the bug. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
