[Bug 1851341] Re: gcc linking fails: undefined reference to sqrt

[Tim Tei]

** Attachment added: "parameters passed to ld on ubuntu"
   https://bugs.launchpad.net/ubuntu/+source/gcc-defaults/+bug/1851341/+attachment/5302953/+files/ubuntu.txt

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Title:
  gcc linking fails: undefined reference to sqrt

Status in gcc-defaults package in Ubuntu:
  New

Bug description:
  The code I try to compile and link:

  $ cat s.c

  #include <stdio.h>
  #include <math.h>

  int main()
  {
          double n = 5.0;
          printf("%f\n", sqrt(n));
  }

  Linking fails with gcc, gcc-7, gcc-8, gcc-9:

  $ gcc -lm s.c
  /usr/bin/ld: /tmp/ccBhhS0F.o: in function `main':
  s.c:(.text+0x23): undefined reference to `sqrt'
  collect2: error: ld returned 1 exit status

  Linking succeeds with g++, clang:

  $ g++ -lm s.c
  $ clang -lm s.c

  Tested with Ubuntu 18.04 and 19.10.

  On Debian linking with gcc works fine.

  The parameters passed to ld differ in Debian and Ubuntu
  (see ld-parameters-ubuntu.txt vs ld-parameters-debian.txt).

  The first "--as-needed" is causing the problems.

  ProblemType: Bug
  DistroRelease: Ubuntu 19.10
  Package: gcc 4:9.2.1-3.1ubuntu1
  ProcVersionSignature: Ubuntu 5.3.0-19.20-generic 5.3.1
  Uname: Linux 5.3.0-19-generic x86_64
  ApportVersion: 2.20.11-0ubuntu8.2
  Architecture: amd64
  CurrentDesktop: ubuntu:GNOME
  Date: Tue Nov  5 08:46:14 2019
  ProcEnviron:
   LANGUAGE=de_DE:
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=de_DE.UTF-8
   SHELL=/bin/bash
  SourcePackage: gcc-defaults
  UpgradeStatus: Upgraded to eoan on 2019-10-29 (6 days ago)

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