hp2ps: Deviation.c:(.text+0x42b): undefined reference to `sqrt'

Start of story is here: http://bugs.gentoo.org/show_bug.cgi?id=293208

In short: LIBM variable is wrongly fulfilled by test:

configure:8389: checking for atan                                                                                              
configure:8389: x86_64-pc-linux-gnu-gcc -o conftest -march=nocona -O2 -pipe  -Wl,-O1 conftest.c -lbfd -liberty  >&5            
conftest.c:109: warning: conflicting types for built-in function 'atan'                                                        
configure:8389: $? = 0

thus test leads to

LIBM=''

, then that sole LIBM passed to hp2ps and hp2ps fails, as no -lbfd -liberty were passed:

gcc -o hp2ps -O -march=native -O2 -pipe -Wa,--noexecstack  -I../../includes
-Wall       AreaBelow.o AuxFile.o Axes.o Curves.o Deviation.o Dimensions.o
Error.o HpFile.o Key.o Main.o Marks.o PsFile.o Reorder.o Scale.o Shade.o
TopTwenty.o TraceElement.o Utilities.o                                          
Deviation.o: In function `Deviation':                                           
Deviation.c:(.text+0x42b): undefined reference to `sqrt'  

AFAIU, before testing for atan presence in -lm ghc should hide his previously found $LIBS, as LIBM is planned to be used separately.

And separate issue: hp2ps (and other utils/) does not seem to respect external LDFLAGS

some spam on #ghc (nothing new):

21:02:36 < trofi> hi, i seem to have found small bunch of bugs in ghc-6.10.4/ghc-6.12
21:03:32 < trofi> I don't like how LIBM variable is detected. It leads to bugs like 
                  http://bugs.gentoo.org/show_bug.cgi?id=293208
21:04:41 < trofi> first test finds atan in absolutely unrelated libs: configure:17837: /usr/bin/gcc -o conftest -g -O2   
                  conftest.c -lbfd -liberty  >&5
21:04:49 < trofi> and decides LIBM=''
21:06:13 < trofi> is it standard autotools practice to grind libraries together?
21:06:36 < trofi> i thought they should be tested separately
21:09:21 < pejo> trofi, so in what library is atan on your OS?
21:10:19 < trofi> libm
21:10:53 < trofi> the problem is autoconf tests not only libm, but libs he found before: -lbfd and -liberty
21:13:04 < trofi> (at a time)
21:13:12 < pejo> What autoconf tests depends on how you've written your tests. If it finds atan in either libiberty or libbdf, 
                 then it doesn't need libm, does it?
21:13:32 < trofi> yes it doesn't
21:13:49 < trofi> but ghc build system does not pass those libraries to build some utils
21:13:55 < trofi> it passes only LIBM
21:14:11 < trofi> which is "obviously" empty
21:14:55 < trofi> it's another bug - when some utils are built there is no respect of user's LDFLAGS variable

Sorry for describing bug in reverse order. Seems like ghc-6.12 is affected too.

Trac metadata

Trac field	Value
Version	6.10.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Build System
Test case
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