Added toolchain support for configuration in prefix headers

This commit uses the previously introduced feature of generating
configuration data as a C header file rather than as command line macro
definitions. Each toolchain was modified to use prefix headers if
requested, and build_api.py was modified to set up the toolchain's
prefix header content using the data generated by the config system.

Tested by compiling blinky for GCC and ARMCC. I'm having a few issues
with my IAR license currently, but both ARMCC and IAR use the same
`--preinclude` option for prefix headers, so this shouldn't be an issue.

Note that at the moment all exporters still use the previous
configuration data mechanism (individual macro definitions as opposed to
a prefix header). Exporters will be updated in one or more PRs that will
follow.

tools/build_api.py

@@ -232,8 +232,8 @@ def build_project(src_path, build_path, target, toolchain_name,
             prev_features = features
         config.validate_config()
 
-        # And add the configuration macros to the toolchain
-        toolchain.add_macros(config.get_config_data_macros())
+        # Set the toolchain's prefix header with the config data
+        toolchain.set_prefix_header_content(config.get_config_data_header())
 
         # Compile Sources
         for path in src_paths:
@@ -403,8 +403,8 @@ def build_library(src_paths, build_path, target, toolchain_name,
             prev_features = features
         config.validate_config()
 
-        # And add the configuration macros to the toolchain
-        toolchain.add_macros(config.get_config_data_macros())
+        # Set the toolchain's prefix header with the config data
+        toolchain.set_prefix_header_content(config.get_config_data_header())
 
         # Compile Sources
         for path in src_paths:

tools/toolchains/__init__.py

@@ -265,6 +265,9 @@ class mbedToolchain:
             
         self.flags = deepcopy(self.DEFAULT_FLAGS)
 
+        # prefix_header_content will hold the content of the prefix header (if used)
+        self.prefix_header_content = None
+
     def get_output(self):
         return self.output
 
@@ -867,6 +870,26 @@ class mbedToolchain:
         map_csv = splitext(map)[0] + "_map.csv"
         memap.generate_output('csv-ci', map_csv)
 
+    # "Prefix headers" are automatically included by the compiler at the beginning of
+    # each source file.
+    # header_content - the content of the prefix header file.
+    def set_prefix_header_content(self, header_content):
+        self.prefix_header_content = header_content
+
+    # Return the location of the prefix header. This function will create the prefix
+    # header first if needed. The header will be written in a file called "mbed_prefix.h"
+    # located in the project's build directory.
+    # If prefix headers are not used (self.prefix_header_content is None), the function
+    # returns None
+    def get_prefix_header(self):
+        if self.prefix_header_content is None:
+            return None
+        prefix_file = join(self.build_dir, "mbed_prefix.h")
+        if not exists(prefix_file):
+            with open(prefix_file, "wt") as f:
+                f.write(self.prefix_header_content)
+        return prefix_file
+
 
 from tools.settings import ARM_BIN
 from tools.settings import GCC_ARM_PATH, GCC_CR_PATH

tools/toolchains/arm.py

@@ -115,7 +115,11 @@ class ARM(mbedToolchain):
         return ["--depend", dep_path]
 
     def get_compile_options(self, defines, includes):        
-        return ['-D%s' % d for d in defines] + ['--via', self.get_inc_file(includes)]
+        opts = ['-D%s' % d for d in defines] + ['--via', self.get_inc_file(includes)]
+        prefix_header = self.get_prefix_header()
+        if prefix_header is not None:
+            opts = opts + ['--preinclude', prefix_header]
+        return opts
 
     @hook_tool
     def assemble(self, source, object, includes):

tools/toolchains/gcc.py

@@ -166,7 +166,11 @@ class GCC(mbedToolchain):
         return ["-MD", "-MF", dep_path]
 
     def get_compile_options(self, defines, includes):
-        return ['-D%s' % d for d in defines] + ['@%s' % self.get_inc_file(includes)]
+        opts = ['-D%s' % d for d in defines] + ['@%s' % self.get_inc_file(includes)]
+        prefix_header = self.get_prefix_header()
+        if prefix_header is not None:
+            opts = opts + ['-include', prefix_header]
+        return opts
 
     @hook_tool
     def assemble(self, source, object, includes):

tools/toolchains/iar.py

@@ -119,7 +119,11 @@ class IAR(mbedToolchain):
         return ["-l", base + '.s.txt']
 
     def get_compile_options(self, defines, includes):
-        return ['-D%s' % d for d in defines] + ['-f', self.get_inc_file(includes)]
+        opts = ['-D%s' % d for d in defines] + ['-f', self.get_inc_file(includes)]
+        prefix_header = self.get_prefix_header()
+        if prefix_header is not None:
+            opts = opts + ['--preinclude', prefix_header]
+        return opts
 
     @hook_tool
     def assemble(self, source, object, includes):