I am using Cygwin.
I found error in C compiler.
error report are as followings :
> g++ -c test.c -o test
> In file included from test.c:1:
> /usr/include/stdio.h:34:20: stddef.h: No such file or directory
> /usr/include/stdio.h:37:20: stdarg.h: No such file or directory
> In file included from /usr/include/sys/reent.h:14,
> from /usr/include/stdio.h:45,
> from test.c:1:
> /usr/include/sys/_types.h:32: error: `wint_t' does not name a type
> In file included from test.c:1:
> /usr/include/stdio.h:176: error: `size_t' has not been declared
> /usr/include/stdio.h:187: error: `__gnuc_va_list' has not been declared
> /usr/include/stdio.h:189: error: `__gnuc_va_list' has not been declared
> : : :
> /usr/include/stdio.h:350: error: expected constructor, destructor, or type conversion before "_fread_r"
> /usr/include/stdio.h:350: error: expected `,' or `;' before "_fread_r"
> : : :
The two main problems are
- missing file stddef.h/stdarg.h ==> I also cannot find in compiler's private directory /usr/lib/gcc/i686-pc-cygwin/3.4.4/include
- it seems have problem in type define : wint_, size_t, ....

I think maybe compiler install not properly, therefore I decide to install gcc again.

When I install gcc, it complaint :
> configure: error: Building GCC requires GMP 4.2+, MPFR 2.3.1+ and MPC 0.8.0+.
> Try the --with-gmp, --with-mpfr and/or --with-mpc options to specify

When I install GMP, it complaint :
> checking build system type... i686-pc-cygwin
> checking host system type... i686-pc-cygwin
> checking for a BSD-compatible install... /usr/bin/install -c
> checking whether build environment is sane... yes
> checking for a thread-safe mkdir -p... /usr/bin/mkdir -p
> checking for gawk... gawk
> checking whether make sets $(MAKE)... no
> checking whether to enable maintainer-specific portions of Makefiles... no
> checking ABI=32
> checking compiler gcc -m32 -O2 -pedantic -fomit-frame-pointer ... no
> checking compiler gcc -O2 -pedantic -fomit-frame-pointer ... no
> checking compiler icc -no-gcc ... no
> checking compiler cc -O ... no
> configure: error: could not find a working compiler, see config.log for details

The content of "config.log" are as followings :
cclist=gcc icc cc
configure:5383: gcc 2>&1 | grep xlc >/dev/null
configure:5386: $? = 1
configure:5440: checking compiler gcc -m32 -O2 -pedantic -fomit-frame-pointer
Test compile:
configure:5454: gcc -m32 -O2 -pedantic -fomit-frame-pointer conftest.c >&5
./configure: line 5455: gcc: command not found
configure:5457: $? = 127
failed program was:

int main () { return 0; }
configure:6480: result: no
configure:5440: checking compiler gcc -O2 -pedantic -fomit-frame-pointer
Test compile:
configure:5454: gcc -O2 -pedantic -fomit-frame-pointer conftest.c >&5
./configure: line 5455: gcc: command not found
configure:5457: $? = 127
failed program was:

int main () { return 0; }
configure:6480: result: no
configure:5361: icc -c conftest.c >&5
./configure: line 5362: icc: command not found
configure:5364: $? = 127
configure:5383: icc 2>&1 | grep xlc >/dev/null
configure:5386: $? = 1
configure:5440: checking compiler icc -no-gcc
Test compile:
configure:5454: icc -no-gcc conftest.c >&5
./configure: line 5455: icc: command not found
configure:5457: $? = 127
failed program was:

int main () { return 0; }
configure:6480: result: no
configure:5361: cc -c conftest.c >&5
./configure: line 5362: cc: command not found
configure:5364: $? = 127
configure:5383: cc 2>&1 | grep xlc >/dev/null
configure:5386: $? = 1
configure:5440: checking compiler cc -O
Test compile:
configure:5454: cc -O conftest.c >&5
./configure: line 5455: cc: command not found
configure:5457: $? = 127
failed program was:

int main () { return 0; }
configure:6480: result: no
configure:6718: error: could not find a working compiler

How come, I miss gcc in Cygwin and so need to install. Now require "gcc" to install GMP?

Which OS you're using? And try to install all the things all over again.

I use Window XP.

I just re-install gcc, since it cannot compile c-code.

Why are you trying to build GCC instead of using cygwin's setup.exe to install it?