Add PCH support for faster building.

.gitignore

@@ -1,4 +1,5 @@
 .deps
+*.gch
 *.lo
 *.loT
 *.la

config.m4

@@ -4,18 +4,54 @@ PHP_ARG_ENABLE(arma,           for armadillo support,
 PHP_ARG_ENABLE(arma-operators, for operator overloading support in armadillo,
 [  --enable-arma-operators  Enable operator overloading for armadillo ], no, no)
 
+PHP_ARG_ENABLE(arma-pch,       build PCH header of armadillo,
+[  --enable-arma-pch        Enable building PCH header of armadillo ], no, no)
+
 if test "$PHP_ARMA" != "no"; then
   PHP_REQUIRE_CXX()
 
-  EXTRA_CXXFLAGS="-std=c++17"
+  # If enabled, try building pre-compiled header for armadillo.
+  if test "$PHP_ARMA_PCH" != "no"; then
+    CXX_INCLEDE_PATHS=($(echo | $CXX -xc++ -E -v - 2>&1 | grep -p '^ /'))
+    PHP_INCLUDES=`php-config --includes`
+    PCH_FILE='./build/armadillo.gch'
+    # Note that '-D' option is valid when compiling PCH header, but not when using it.
+    CXX_TMP_COMPILE_FLAGS="-std=c++17 -x c++-header $PHP_INCLUDES -DARMA_DONT_PRINT_ERRORS"
+    if test -z "$PHP_DEBUG"; then
+      CXX_TMP_COMPILE_FLAGS+=' -O2'
+    else
+      CXX_TMP_COMPILE_FLAGS+=' -g -O0'
+    fi
+  fi
+  for TEMP_INCLUDE_DIR in "$CXX_INCLEDE_PATHS"; do
+    ARMADILLO_HEADER_FILE=$TEMP_INCLUDE_DIR/armadillo
+    if test -f "$ARMADILLO_HEADER_FILE"; then
+      $CXX $CXX_TMP_COMPILE_FLAGS $TEMP_INCLUDE_DIR/armadillo -o $PCH_FILE
+      break
+    fi
+  done
+
+  # Include PCH file if valid.
+  EXTRA_CXXFLAGS="-std=c++17 -DARMA_DONT_PRINT_ERRORS"
   CLANG_TEST_STR=`$CXX --version | grep clang`
-  if test -n "$CLANG_TEST_STR"; then
-    EXTRA_CXXFLAGS+=" -Wno-undefined-var-template -Wno-deprecated-declarations"
+  if test -f "$PCH_FILE"; then
+    if test -n "$CLANG_TEST_STR"; then
+      EXTRA_CXXFLAGS+=" -include-pch $PCH_FILE"
+      # Define this only for clang, in gcc we still need the include directive.
+      AC_DEFINE(PHP_ARMA_ENABLE_PCH, 1, [ Defined if using pre-compiled armadillo header. ])
+    else
+      EXTRA_CXXFLAGS+=' -I./build'
+    fi
   fi
 
+  # Disable some clang warnings we don't care.
+  if test -n "$CLANG_TEST_STR"; then
+    EXTRA_CXXFLAGS+=' -Wno-undefined-var-template -Wno-deprecated-declarations'
+  fi
+
+  # Enable/disable operator overloading support.
   OPERATORS_SRC="src/operators.cc"
   ARMA_SRC=`ls -1d src/*.cc | grep -v $OPERATORS_SRC`
-
   if test "$PHP_ARMA_OPERATORS" != "no"; then
     AC_DEFINE(PHP_ARMA_OPERATORS, 1, [ Defined if operator overloading is enabled for armadillo. ])
     ARMA_SRC+=" $OPERATORS_SRC"

src/operators.cc

@@ -4,7 +4,6 @@
 // @Author CismonX
 //
 
-#include "php_arma.hh"
 #include "operators.hh"
 #include "complex.hh"
 #include "base.hh"

src/php_arma.hh

@@ -14,7 +14,9 @@
 #include <php.h>
 #include <zend_exceptions.h>
 
+#ifndef PHP_ARMA_ENABLE_PCH
 #include <armadillo>
+#endif
 
 #define PHP_ARMA_VERSION         "0.0.1"
 
@@ -22,8 +24,6 @@
 #define ZEND_ACC_CTOR            0
 #endif
 
-#define ARMA_DONT_PRINT_ERRORS
-
 /// Helper macros for method entry.
 
 #define PHP_ARMA_START_ME(cls, ...)                       \