[GHC] #11137: configure is broken for the unix package

[GHC]

#11137: configure is broken for the unix package
-------------------------------------+-------------------------------------
           Reporter:  pgj            |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:                 |           Version:  7.11
  libraries/unix                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Building GHC
  Unknown/Multiple                   |  failed
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 A few weeks ago (around November 1, 2015), the FreeBSD builders started to
 fail building GHC-HEAD with an error message something like that:

 {{{
 [...]
 /usr/home/ghc-builder/work/builder/tempbuild/build/libraries/unix/dist-
 install/build/libHSunix-2.7.1.0-ghc7.11.20151126.so: undefined reference
 to `fdatasync'
 collect2: error: ld returned 1 exit status
 `gcc48' failed in phase `Linker'. (Exit code: 1)
 ghc/ghc.mk:121: recipe for target 'ghc/stage2/build/tmp/ghc-stage2' failed
 gmake[1]: *** [ghc/stage2/build/tmp/ghc-stage2] Error 1
 Makefile:121: recipe for target 'all' failed
 gmake: *** [all] Error 2
 }}}

 That is because {{{fdatasync(2)}}} is not implemented on FreeBSD.
 Apparently, it is handled in the respective file
 ({{{System/Posix/Unistd.hsc}}}), though it relies on the variable
 ({{{HAVE_FDATASYNC}}}) generated at the {{{configure}}} phase.  But for
 some reason, the {{{configure}}} script of the {{{unix}}} package fails to
 detect this as it says the following:

 {{{
 "inplace/bin/ghc-cabal" configure libraries/unix dist-install "" --with-
 ghc="/usr/home/ghc-builder/work/builder/tempbuild/build/inplace/bin/ghc-
 stage1" --with-ghc-pkg="/usr/home/ghc-
 builder/work/builder/tempbuild/build/inplace/bin/ghc-pkg"  --disable-
 library-for-ghci --enable-library-vanilla --enable-library-profiling
 --enable-shared --with-hscolour="/usr/local/bin/HsColour" --configure-
 option=CFLAGS="-Wall -fno-stack-protector    -Werror=unused-but-set-
 variable -Wno-error=inline" --configure-option=LDFLAGS="  " --configure-
 option=CPPFLAGS="   " --gcc-options="-Wall -fno-stack-protector    -Werror
 =unused-but-set-variable -Wno-error=inline   " --configure-option=--with-
 iconv-includes="/usr/local/include" --configure-option=--with-iconv-
 libraries="/usr/local/lib" --configure-option=--with-gmp-
 includes="/usr/local/include" --configure-option=--with-gmp-
 libraries="/usr/local/lib" --with-gcc="/usr/local/bin/gcc48" --with-
 ld="/usr/local/bin/ld" --configure-option=--with-cc="/usr/local/bin/gcc48"
 --with-ar="/usr/local/bin/ar" --with-alex="/usr/local/bin/alex" --with-
 happy="/usr/local/bin/happy"
 Configuring unix-2.7.1.0...
 [...]
 checking for fdatasync... yes
 }}}

 That is the corresponding part of the {{{config.log}}}:

 {{{
 configure:4242: checking for fdatasync
 configure:4263: /usr/local/bin/gcc48 -c -Wall -fno-stack-protector
 -Werror=unused-but-set-variable -Wno-error=inline     conftest.c >&5
 conftest.c: In function 'main':
 conftest.c:71:1: warning: implicit declaration of function 'fdatasync'
 [-Wimplicit-function-declaration]
  fdatasync(4);
  ^
 configure:4263: $? = 0
 configure:4271: result: yes
 }}}

 Looks like GCC is willing to compile the test code, although it notes that
 it cannot find the declaration of the {{{fdatasync()}}} function.
 Unfortunately, the {{{configure}}} script does not instruct GCC to do any
 linking or be serious on such warnings, so it happily proceeds.

 For the reference, previously the {{{config.log}}} said something like
 that instead:

 {{{
 configure:4230: checking for fdatasync
 configure:4230: /usr/local/bin/gcc48 -o conftest -Wall -fno-stack-
 protector    -Werror=unused-but-set-variable -Wno-error=inline
 conftest.c  >&5
 /tmp//ccDCjZtO.o: In function `main':
 conftest.c:(.text+0xa): undefined reference to `fdatasync'
 collect2: error: ld returned 1 exit status
 configure:4230: $? = 1
 [...]
 }}}

 I am inclined to think that this is caused by the commit
 [https://github.com/haskell/unix/commit/b06446edd4753f964a46d27ddae864fad97adc13
 b06446edd4753f964a46d27ddae864fad97adc13] for the {{{unix}}} package.
 Perhaps the following change can fix that, at least it fixed for me:

 {{{
 --- a/mk/warnings.mk
 +++ b/mk/warnings.mk
 @@ -16,6 +16,7 @@ SRC_CC_WARNING_OPTS += -Werror=unused-but-set-variable
  endif
  # gcc 4.6 gives 3 warning for giveCapabilityToTask not being inlined
  SRC_CC_WARNING_OPTS += -Wno-error=inline
 +SRC_CC_WARNING_OPTS += -Werror=implicit-function-declaration
  endif

  else
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11137>
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