diff options
Diffstat (limited to 'Documentation/kbuild/makefiles.txt')
| -rw-r--r-- | Documentation/kbuild/makefiles.txt | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index 54bbfd37f157..1ca535bcc8c7 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt | |||
| @@ -294,7 +294,7 @@ more details, with real examples. | |||
| 294 | 294 | ||
| 295 | 295 | ||
| 296 | This variable is necessary because the top Makefile owns the | 296 | This variable is necessary because the top Makefile owns the |
| 297 | variable $(CFLAGS) and uses it for compilation flags for the | 297 | variable $(KBUILD_CFLAGS) and uses it for compilation flags for the |
| 298 | entire tree. | 298 | entire tree. |
| 299 | 299 | ||
| 300 | $(EXTRA_AFLAGS) is a similar string for per-directory options | 300 | $(EXTRA_AFLAGS) is a similar string for per-directory options |
| @@ -437,6 +437,7 @@ more details, with real examples. | |||
| 437 | -march=pentium-mmx if supported by $(CC), otherwise -march=i586. | 437 | -march=pentium-mmx if supported by $(CC), otherwise -march=i586. |
| 438 | The second argument to cc-option is optional, and if omitted, | 438 | The second argument to cc-option is optional, and if omitted, |
| 439 | cflags-y will be assigned no value if first option is not supported. | 439 | cflags-y will be assigned no value if first option is not supported. |
| 440 | Note: cc-option uses KBUILD_CFLAGS for $(CC) options | ||
| 440 | 441 | ||
| 441 | cc-option-yn | 442 | cc-option-yn |
| 442 | cc-option-yn is used to check if gcc supports a given option | 443 | cc-option-yn is used to check if gcc supports a given option |
| @@ -452,6 +453,7 @@ more details, with real examples. | |||
| 452 | option. When $(biarch) equals 'y', the expanded variables $(aflags-y) | 453 | option. When $(biarch) equals 'y', the expanded variables $(aflags-y) |
| 453 | and $(cflags-y) will be assigned the values -a32 and -m32, | 454 | and $(cflags-y) will be assigned the values -a32 and -m32, |
| 454 | respectively. | 455 | respectively. |
| 456 | Note: cc-option-yn uses KBUILD_CFLAGS for $(CC) options | ||
| 455 | 457 | ||
| 456 | cc-option-align | 458 | cc-option-align |
| 457 | gcc versions >= 3.0 changed the type of options used to specify | 459 | gcc versions >= 3.0 changed the type of options used to specify |
| @@ -463,10 +465,11 @@ more details, with real examples. | |||
| 463 | cc-option-align = -falign | 465 | cc-option-align = -falign |
| 464 | 466 | ||
| 465 | Example: | 467 | Example: |
| 466 | CFLAGS += $(cc-option-align)-functions=4 | 468 | KBUILD_CFLAGS += $(cc-option-align)-functions=4 |
| 467 | 469 | ||
| 468 | In the above example, the option -falign-functions=4 is used for | 470 | In the above example, the option -falign-functions=4 is used for |
| 469 | gcc >= 3.00. For gcc < 3.00, -malign-functions=4 is used. | 471 | gcc >= 3.00. For gcc < 3.00, -malign-functions=4 is used. |
| 472 | Note: cc-option-align uses KBUILD_CFLAGS for $(CC) options | ||
| 470 | 473 | ||
| 471 | cc-version | 474 | cc-version |
| 472 | cc-version returns a numerical version of the $(CC) compiler version. | 475 | cc-version returns a numerical version of the $(CC) compiler version. |
| @@ -825,17 +828,17 @@ When kbuild executes, the following steps are followed (roughly): | |||
| 825 | #arch/sparc64/Makefile | 828 | #arch/sparc64/Makefile |
| 826 | AFLAGS += -m64 -mcpu=ultrasparc | 829 | AFLAGS += -m64 -mcpu=ultrasparc |
| 827 | 830 | ||
| 828 | CFLAGS $(CC) compiler flags | 831 | KBUILD_CFLAGS $(CC) compiler flags |
| 829 | 832 | ||
| 830 | Default value - see top level Makefile | 833 | Default value - see top level Makefile |
| 831 | Append or modify as required per architecture. | 834 | Append or modify as required per architecture. |
| 832 | 835 | ||
| 833 | Often, the CFLAGS variable depends on the configuration. | 836 | Often, the KBUILD_CFLAGS variable depends on the configuration. |
| 834 | 837 | ||
| 835 | Example: | 838 | Example: |
| 836 | #arch/i386/Makefile | 839 | #arch/i386/Makefile |
| 837 | cflags-$(CONFIG_M386) += -march=i386 | 840 | cflags-$(CONFIG_M386) += -march=i386 |
| 838 | CFLAGS += $(cflags-y) | 841 | KBUILD_CFLAGS += $(cflags-y) |
| 839 | 842 | ||
| 840 | Many arch Makefiles dynamically run the target C compiler to | 843 | Many arch Makefiles dynamically run the target C compiler to |
| 841 | probe supported options: | 844 | probe supported options: |
| @@ -847,7 +850,7 @@ When kbuild executes, the following steps are followed (roughly): | |||
| 847 | -march=pentium2,-march=i686) | 850 | -march=pentium2,-march=i686) |
| 848 | ... | 851 | ... |
| 849 | # Disable unit-at-a-time mode ... | 852 | # Disable unit-at-a-time mode ... |
| 850 | CFLAGS += $(call cc-option,-fno-unit-at-a-time) | 853 | KBUILD_CFLAGS += $(call cc-option,-fno-unit-at-a-time) |
| 851 | ... | 854 | ... |
| 852 | 855 | ||
| 853 | 856 | ||
