LUFA/Build/DMBS/DMBS/gcc.md

   1 DMBS - Dean's Makefile Build System
   2 ===================================
   3
   4
   5 Module: GCC
   6 -----------------
   7
   8 The GCC module provides build targets to compile a user application, using a
   9 variant of GCC for a specific target architecture (such as `avr-gcc`).
  10
  11 ## Importing This Module into a Makefile:
  12
  13 To use this module in your application makefile, add the following code to your
  14 makefile:
  15
  16     include $(DMBS_PATH)/gcc.mk
  17
  18 ## Prerequisites:
  19
  20 This module requires the GCC compiler to be installed and available in the
  21 system's `PATH` variable for the desired target architecture.
  22
  23 ## Build Targets:
  24
  25 The following targets are supported by this module:
  26
  27 <table>
  28  <tbody>
  29    <tr>
  30     <td>size</td>
  31     <td>Show the compiled binary size for the various memory segments.</td>
  32    </tr>
  33    <tr>
  34     <td>symbol-sizes</td>
  35     <td>Show the size of each symbol in the compiled binary (useful to find large functions to optimize further).</td>
  36    </tr>
  37    <tr>
  38     <td>all</td>
  39     <td>Build application and generate all binary (BIN, ELF, HEX) and auxiliary (LSS, MAP, SYM, etc.) output files.</td>
  40    </tr>
  41    <tr>
  42     <td>lib</td>
  43     <td>Generate a static `.a` library from the application code, containing the flash region's data.</td>
  44    </tr>
  45    <tr>
  46     <td>elf</td>
  47     <td>Generate an ELF debug file from the application code, containing all region's data.</td>
  48    </tr>
  49    <tr>
  50     <td>bin</td>
  51     <td>Generate a flat BIN binary file from the application code, containing the flash region's data.</td>
  52    </tr>
  53    <tr>
  54     <td>hex</td>
  55     <td>Generate a pair of Intel HEX files from the application code, containing the flash region's data (HEX) and EEPROM data (EEP).</td>
  56    </tr>
  57    <tr>
  58     <td>lss</td>
  59     <td>Generate a LSS listing file showing the disassembly of the compiled application.</td>
  60    </tr>
  61    <tr>
  62     <td>clean</td>
  63     <td>Remove all generated project intermediary and binary output files.</td>
  64    </tr>
  65    <tr>
  66     <td>mostlyclean</td>
  67     <td>Remove all generated project intermediary output files, but preserve the binary output files.</td>
  68    </tr>
  69  </tbody>
  70 </table>
  71
  72 ## Mandatory Variables:
  73
  74 The following variables must be defined (with a `NAME = VALUE` syntax, one
  75 variable per line) in the user makefile to be able to use this module:
  76
  77 <table>
  78  <tbody>
  79    <tr>
  80     <td>MCU</td>
  81     <td>Name of the Atmel processor model (e.g. `at90usb1287`).</td>
  82    </tr>
  83    <tr>
  84     <td>TARGET</td>
  85     <td>Name of the application output file prefix (e.g. `TestApplication`).</td>
  86    </tr>
  87    <tr>
  88     <td>ARCH</td>
  89     <td>Target device architecture (e.g. `AVR8`).</td>
  90    </tr>
  91    <tr>
  92      <td>SRC</td>
  93      <td>List of all project source files (C, C++, ASM).</td>
  94    </tr>
  95  </tbody>
  96 </table>
  97
  98 ## Optional Variables:
  99
 100 The following variables may be defined (with a `NAME = VALUE` syntax, one
 101 variable per line) in the user makefile. If not specified, a default value will
 102 be assumed.
 103
 104 <table>
 105  <tbody>
 106    <tr>
 107     <td>COMPILER_PATH</td>
 108     <td>Path to the compiler to use, in case a specific compiler should be substituted for the one in the system's `PATH` variable. Default is blank (use `PATH` provided compiler).</td>
 109    </tr>
 110    <tr>
 111     <td>OPTIMIZATION</td>
 112     <td>Optimization level to use when compiling C and C++ source files. Default is `s` (optimize for smallest size).</td>
 113    </tr>
 114    <tr>
 115     <td>C_STANDARD</td>
 116     <td>C language standard used when compiling C language source files. Default is `gnu99` (C99 standard with GNU extensions)./td>
 117    </tr>
 118    <tr>
 119     <td>CPP_STANDARD</td>
 120     <td>C++ language standard used when compiling C++ language source files. Default is `gnu++11` (C++11 standard with GNU extensions)./td>
 121    </tr>
 122    <tr>
 123     <td>F_CPU</td>
 124     <td>Processor core clock frequency, in Hz. This is used by some architectures for functions such as software spin-loop delays. Default is blank (no value defined).</td>
 125    </tr>
 126    <tr>
 127     <td>C_FLAGS</td>
 128     <td>Common GCC flags passed to the compiler for C language (C) input files. Default is blank (no additional flags).</td>
 129    </tr>
 130    <tr>
 131     <td>CPP_FLAGS</td>
 132     <td>Common GCC flags passed to the compiler for C++ language (CPP) input files. Default is blank (no additional flags).</td>
 133    </tr>
 134    <tr>
 135     <td>ASM_FLAGS</td>
 136     <td>Common GCC flags passed to the assembler for assembly language (S) input files. Default is blank (no additional flags).</td>
 137    </tr>
 138    <tr>
 139     <td>CC_FLAGS</td>
 140     <td>Common GCC flags passed to the compiler for all source file types. Default is blank (no additional flags).</td>
 141    </tr>
 142    <tr>
 143     <td>LD_FLAGS</td>
 144     <td>Extra flags to pass to the GNU linker when linking the compiled object files into the resulting binary. Default is blank (no additional flags).</td>
 145    </tr>
 146    <tr>
 147     <td>LINKER_RELAXATIONS</td>
 148     <td>Boolean, if `Y` linker relaxations will be enabled to slightly reduce the resulting binary's size. Default is `Y`.</td>
 149    </tr>
 150    <tr>
 151     <td>JUMP_TABLES</td>
 152     <td>Boolean, if `Y` jump tables will be enabled to slightly reduce the resulting binary's size - note that this can cause incorrect jumps if the binary is relocated after compilation, such as for a bootloader. Default is `N`.</td>
 153    </tr>
 154    <tr>
 155     <td>LTO</td>
 156     <td>Boolean, if `Y` link time optimization will be enabled to reduce the resulting binary's size. For larger projects you might also want to add `-mcall-prologues` to the `CC_FLAGS`. Default is `N`.</td>
 157    </tr>
 158    <tr>
 159     <td>OBJDIR</td>
 160     <td>Directory to store the intermediate object files, as they are generated from the source files. Default is `obj`.</td>
 161    </tr>
 162    <tr>
 163     <td>OBJECT_FILES</td>
 164     <td>List of additional `.o` object files to link into the final binary. Default is blank (no additional objects).</td>
 165    </tr>
 166    <tr>
 167     <td>DEBUG_FORMAT</td>
 168     <td>Debug ELF file format to generate. Default is `dwarf-2`.</td>
 169    </tr>
 170    <tr>
 171     <td>DEBUG_LEVEL</td>
 172     <td>Level of the debugging information to generate in the compiled object files. Debug is 2 (medium level debugging information).</td>
 173    </tr>
 174  </tbody>
 175 </table>
 176
 177 ## Provided Variables:
 178
 179 The following variables may be referenced in a user makefile (via `$(NAME)`
 180 syntax) if desired, as they are provided by this module.
 181
 182 <table>
 183  <tbody>
 184    <tr>
 185     <td>N/A</td>
 186     <td>This module provides no variables.</td>
 187    </tr>
 188  </tbody>
 189 </table>
 190
 191 ## Provided Macros:
 192
 193 The following macros may be referenced in a user makefile (via
 194 `$(call NAME, ARG1, ARG2, ...)` syntax) if desired, as they are provided by
 195 this module.
 196
 197 <table>
 198  <tbody>
 199    <tr>
 200     <td>N/A</td>
 201     <td>This module provides no macros.</td>
 202    </tr>
 203  </tbody>
 204 </table>
 205
 206 ## Module Changelog:
 207
 208 The changes to this module since its initial release are listed below, as of the
 209 DMBS version where the change was made.
 210
 211 ### 20180122
 212 Changed C++ default language standard from gnu++98 to gnu++11.
 213
 214 ### 20171231
 215 Added `-fpack-struct` for C files only (not C++).
 216 Added `-fno-exceptions` and `-fno-threadsafe-statics` for C++ source files.
 217 Added file-specific compilation flags.
 218 Added `LTO` optional variable.
 219
 220 ### 20170426
 221 Added `JUMP_TABLES` optional variable.
 222
 223 ### 20160403
 224 Initial release.