autoconf-2.57: AC_C_LONG_DOUBLE test fails with Sun Solaris 10 c99 compiler

[Nelson H. F. Beebe]

The test code generated for AC_C_LONG_DOUBLE in autoconf-2.57 fails
with the Sun Solaris 10 Studio 9 C and C++ compilers in these five
environments:

        CC=/opt/studio9/SUNWspro/bin/cc
        CFLAGS="-xc99=%all -I/usr/local/include -D_XOPEN_SOURCE=600"

        CC=/opt/studio9/SUNWspro/bin/c89
        CFLAGS=-I/usr/local/include

        CC=/opt/studio9/SUNWspro/bin/CC
        CFLAGS=-I/usr/local/include

        CC=/opt/studio9/SUNWspro/bin/cc
        CFLAGS=-I/usr/local/include

        CC=/opt/studio9/SUNWspro/bin/c99
        CFLAGS="-I/usr/local/include"

These compilers all report these versions:

        cc: Sun C 5.6 2004/06/02
        CC: Sun C++ 5.6 2004/06/02

The config.log file extract looks like this:

        configure:2822: /opt/studio9/SUNWspro/bin/cc -c -xc99=%all 
-I/usr/local/include -D_XOPEN_SOURCE=600
         conftest.c >&5
        "configure", line 2841: variable length array can not be declared with 
a static storage class:
        test_array
        cc: acomp failed for conftest.c
        configure:2825: $? = 2
        configure: failed program was:
        ...
        | int
        | main ()
        | {
        | static int test_array [1 - 2 * !(/* Using '|' rather than '||' 
catches a GCC 2.95.2 x86 bug.  */
        |           (DBL_MAX < LDBL_MAX) | (LDBL_EPSILON < DBL_EPSILON)
        |         | (DBL_MAX_EXP < LDBL_MAX_EXP) | (DBL_MANT_DIG < 
LDBL_MANT_DIG))];
        | test_array [0] = 0
        |
        |   ;
        |   return 0;
        | }

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- Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
- University of Utah                    FAX: +1 801 581 4148                  -
- Department of Mathematics, 110 LCB    Internet e-mail: address@hidden  -
- 155 S 1400 E RM 233                       address@hidden  address@hidden -
- Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe  -
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