minor

README.html

@@ -98,6 +98,8 @@
   <div class="codeline">make -j8</div>
   <p>To build all programs (into either <code>bin/unix</code> or <code>bin/win</code>) and run all unit tests:</p>
   <div class="codeline">make -j test</div>
+  <p>To build on Unix, forcing the use of the <code>gcc</code> compiler (the alternative is <code>clang</code>):</p>
+  <div class="codeline">make CC=gcc -j</div>
   <p>To build just the main library using the <code>mingw gcc</code> compiler on Windows:</p>
   <div class="codeline">make CONFIG=mingw -j libHh</div>
   <p>To build the <code>Filtermesh</code> program (into <code>bin/clang</code>) using the <code>clang</code> compiler on Windows:</p>

make/Makefile_config_unix

@@ -9,9 +9,9 @@ ifeq ($(is_mac),1)
   LDFLAGS += -L/opt/X11/lib#      for XQuartz X11
   cppinc += -Wno-variadic-macros# ignore warning in <X11/Xlib.h>
   std_c++ ?= -std=c++11#  override default -std=c++14; necessary for older Xcode versions (e.g. 5.0)
-  CC ?= clang#  set default choice of compiler (clang or gcc)
+  CC = clang#  set default choice of compiler (clang or gcc); override using "make CC=new ..."
 else
-  CC ?= gcc#  set default choice of compiler (clang or gcc)
+  CC = gcc#  set default choice of compiler (clang or gcc); override using "make CC=new ..."
 endif
 
 include $(dir $(lastword $(MAKEFILE_LIST)))/Makefile_base_$(CC)