how to debug configure.sh errors when compiling rsync on Yosemite I am trying to build myself a new version of rsync 3.1.1 under Mac OS 10.10.3, as the mac comes with an older version, and the project does not distribute binaries.

I followed this simple script but it hiccups on gcc. (I am not sure why — though I removed XCode to save disk space, I have the command line tools, incl. gcc in /usr/bin etc.) I would try to build it with clang instead, but how exactly shall I do that?

Here is the error from the script:

configure.sh: Configuring rsync 3.1.1
checking build system type... x86_64-apple-darwin14.3.0
checking host system type... x86_64-apple-darwin14.3.0
checking whether to include debugging
symbols... yes
checking for gcc... gcc
checking whether the C compiler works... no
configure.sh: error: in `/Users/laszlosandor/Downloads/rsync-3.1.1':
configure.sh: error: C
compiler cannot create executable
See `config.log' for more details
make: *** No targets specified and no makefile found.  Stop.


Or even more from the relevant sections of config.log:

gcc: warning: couldn't understand kern.osversion '14.3.0
configure.sh:2893: $? = 0
configure.sh:2882: gcc -v &gt;&amp;5
gcc: warning: couldn't understand kern.osversion '14.3.0
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-apple-darwin12.2.0/4.8.0/lto-wrapper
Target: x86_64-apple-darwin12.2.0
Configured with: ../gcc-4.8-20120930/configure --enable-languages=c++,fortran
Thread model: posix
gcc version 4.8.0 20120930 (experimental) (GCC) 
configure.sh:2893: $? = 0
configure.sh:2882: gcc -V &gt;&amp;5
gcc: warning: couldn't understand kern.osversion '14.3.0
gcc: error: unrecognized command line option '-V'
gcc: fatal error: no input files
compilation terminated.
configure.sh:2893: $? = 1
configure.sh:2882: gcc -qversion &gt;&amp;5
gcc: warning: couldn't understand kern.osversion '14.3.0
gcc: error: unrecognized command line option '-qversion'
gcc: fatal error: no input files
compilation terminated.
configure.sh:2893: $? = 1
configure.sh:2913: checking whether the C compiler works
configure.sh:2935: gcc    conftest.c  &gt;&amp;5
gcc: warning: couldn't understand kern.osversion '14.3.0
ld: library not found for -lgcc_ext.10.4
collect2: error: ld returned 1 exit status
configure.sh:2939: $? = 1
configure.sh:2977: result: no
configure.sh: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME ""
| #define PACKAGE_TARNAME ""
| #define PACKAGE_VERSION ""
| #define PACKAGE_STRING ""
| #define PACKAGE_BUGREPORT ""
| #define PACKAGE_URL ""
| #define RSYNC_VERSION "3.1.1"
| /* end confdefs.h.  */
| 
| int
| main ()
| {
| 
|   ;
|   return 0;
| }
configure.sh:2982: error: in `/Users/laszlosandor/Downloads/rsync-3.1.1':
configure.sh:2984: error: C compiler cannot create executables
See `config.log' for more details


By the way, I know I could have just stuck with Homebrew, but now I want to learn.
The problem is with the install of the command-line developer tools on your Mac.

Try installing again with the following command. This should install the command-line tools alone.

 xcode-select --install


The script is testing the command-line tools to see whether a compatible version is installed but is getting back confusing responses. This is why it fails.