aba31cb691
The C standard undefines behavior when signed integers overflow. The compiler toolchain has become more adept at detecting this and taking advantage of faster undefined behavior. At the current time this has the unfortunate effect of the clock stopping after 24 days of uptime. clang makes no distinction between -fwrapv and -fno-strict-overflow. gcc does treat them differently but -fwrapv is mature in gcc and is the behavior are actually expecting. Obtained from: kib
217 lines
7.3 KiB
Makefile
217 lines
7.3 KiB
Makefile
# $FreeBSD$
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#
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# Warning flags for compiling the kernel and components of the kernel:
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#
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CWARNFLAGS?= -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
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-Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
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-Wundef -Wno-pointer-sign ${FORMAT_EXTENSIONS} \
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-Wmissing-include-dirs -fdiagnostics-show-option \
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-Wno-unknown-pragmas \
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${CWARNEXTRA}
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#
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# The following flags are next up for working on:
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# -Wextra
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# Disable a few warnings for clang, since there are several places in the
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# kernel where fixing them is more trouble than it is worth, or where there is
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# a false positive.
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.if ${COMPILER_TYPE} == "clang"
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NO_WCONSTANT_CONVERSION= -Wno-constant-conversion
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NO_WSHIFT_COUNT_NEGATIVE= -Wno-shift-count-negative
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NO_WSHIFT_COUNT_OVERFLOW= -Wno-shift-count-overflow
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NO_WSELF_ASSIGN= -Wno-self-assign
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NO_WUNNEEDED_INTERNAL_DECL= -Wno-unneeded-internal-declaration
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NO_WSOMETIMES_UNINITIALIZED= -Wno-error-sometimes-uninitialized
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NO_WCAST_QUAL= -Wno-cast-qual
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# Several other warnings which might be useful in some cases, but not severe
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# enough to error out the whole kernel build. Display them anyway, so there is
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# some incentive to fix them eventually.
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CWARNEXTRA?= -Wno-error-tautological-compare -Wno-error-empty-body \
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-Wno-error-parentheses-equality -Wno-error-unused-function \
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-Wno-error-pointer-sign
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CLANG_NO_IAS= -no-integrated-as
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.if ${COMPILER_VERSION} < 30500
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# XXX: clang < 3.5 integrated-as doesn't grok .codeNN directives
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CLANG_NO_IAS34= -no-integrated-as
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.endif
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.endif
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.if ${COMPILER_TYPE} == "gcc"
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GCC_MS_EXTENSIONS= -fms-extensions
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.if ${COMPILER_VERSION} >= 40300
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# Catch-all for all the things that are in our tree, but for which we're
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# not yet ready for this compiler. Note: we likely only really "support"
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# building with gcc 4.8 and newer. Nothing older has been tested.
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CWARNEXTRA?= -Wno-error=inline -Wno-error=enum-compare -Wno-error=unused-but-set-variable \
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-Wno-error=aggressive-loop-optimizations -Wno-error=maybe-uninitialized \
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-Wno-error=array-bounds -Wno-error=address \
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-Wno-error=cast-qual -Wno-error=sequence-point -Wno-error=attributes \
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-Wno-error=strict-overflow -Wno-error=overflow
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.else
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# For gcc 4.2, eliminate the too-often-wrong warnings about uninitialized vars.
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CWARNEXTRA?= -Wno-uninitialized
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.endif
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.endif
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# External compilers may not support our format extensions. Allow them
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# to be disabled. WARNING: format checking is disabled in this case.
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.if ${MK_FORMAT_EXTENSIONS} == "no"
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FORMAT_EXTENSIONS= -Wno-format
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.else
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FORMAT_EXTENSIONS= -fformat-extensions
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.endif
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#
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# On i386, do not align the stack to 16-byte boundaries. Otherwise GCC 2.95
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# and above adds code to the entry and exit point of every function to align the
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# stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
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# per function call. While the 16-byte alignment may benefit micro benchmarks,
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# it is probably an overall loss as it makes the code bigger (less efficient
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# use of code cache tag lines) and uses more stack (less efficient use of data
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# cache tag lines). Explicitly prohibit the use of FPU, SSE and other SIMD
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# operations inside the kernel itself. These operations are exclusively
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# reserved for user applications.
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#
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# gcc:
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# Setting -mno-mmx implies -mno-3dnow
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# Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
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#
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# clang:
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# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
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# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
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#
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.if ${MACHINE_CPUARCH} == "i386"
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CFLAGS.gcc+= -mno-align-long-strings -mpreferred-stack-boundary=2
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CFLAGS.clang+= -mno-aes -mno-avx
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CFLAGS+= -mno-mmx -mno-sse -msoft-float
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INLINE_LIMIT?= 8000
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.endif
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.if ${MACHINE_CPUARCH} == "arm"
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INLINE_LIMIT?= 8000
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.endif
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#
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# For sparc64 we want the medany code model so modules may be located
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# anywhere in the 64-bit address space. We also tell GCC to use floating
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# point emulation. This avoids using floating point registers for integer
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# operations which it has a tendency to do.
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#
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.if ${MACHINE_CPUARCH} == "sparc64"
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CFLAGS.clang+= -mcmodel=large -fno-dwarf2-cfi-asm
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CFLAGS.gcc+= -mcmodel=medany -msoft-float
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INLINE_LIMIT?= 15000
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.endif
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#
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# For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
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# operations inside the kernel itself. These operations are exclusively
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# reserved for user applications.
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#
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# gcc:
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# Setting -mno-mmx implies -mno-3dnow
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# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
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#
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# clang:
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# Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
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# Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
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# (-mfpmath= is not supported)
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#
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.if ${MACHINE_CPUARCH} == "amd64"
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CFLAGS.clang+= -mno-aes -mno-avx
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CFLAGS+= -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \
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-fno-asynchronous-unwind-tables
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INLINE_LIMIT?= 8000
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.endif
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#
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# For PowerPC we tell gcc to use floating point emulation. This avoids using
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# floating point registers for integer operations which it has a tendency to do.
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# Also explicitly disable Altivec instructions inside the kernel.
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#
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.if ${MACHINE_CPUARCH} == "powerpc"
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CFLAGS+= -msoft-float -mno-altivec
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INLINE_LIMIT?= 15000
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.endif
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#
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# Use dot symbols on powerpc64 to make ddb happy
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#
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.if ${MACHINE_ARCH} == "powerpc64"
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CFLAGS+= -mcall-aixdesc
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.endif
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#
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# For MIPS we also tell gcc to use floating point emulation
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#
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.if ${MACHINE_CPUARCH} == "mips"
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CFLAGS+= -msoft-float
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INLINE_LIMIT?= 8000
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.endif
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#
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# GCC 3.0 and above like to do certain optimizations based on the
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# assumption that the program is linked against libc. Stop this.
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#
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CFLAGS+= -ffreestanding
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#
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# The C standard leaves signed integer overflow behavior undefined.
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# gcc and clang opimizers take advantage of this. The kernel makes
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# use of signed integer wraparound mechanics so we need the compiler
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# to treat it as a wraparound and not take shortcuts.
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#
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CFLAGS+= -fwrapv
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#
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# GCC SSP support
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#
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.if ${MK_SSP} != "no" && \
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${MACHINE_CPUARCH} != "arm" && ${MACHINE_CPUARCH} != "mips"
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CFLAGS+= -fstack-protector
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.endif
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#
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# Add -gdwarf-2 when compiling -g. The default starting in clang v3.4
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# and gcc 4.8 is to generate DWARF version 4. However, our tools don't
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# cope well with DWARF 4, so force it to genereate DWARF2, which they
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# understand. Do this unconditionally as it is harmless when not needed,
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# but critical for these newer versions.
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#
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.if ${CFLAGS:M-g} != "" && ${CFLAGS:M-gdwarf*} == ""
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CFLAGS+= -gdwarf-2
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.endif
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CFLAGS+= ${CWARNEXTRA} ${CWARNFLAGS} ${CWARNFLAGS.${.IMPSRC:T}}
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CFLAGS+= ${CFLAGS.${COMPILER_TYPE}} ${CFLAGS.${.IMPSRC:T}}
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# Tell bmake not to mistake standard targets for things to be searched for
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# or expect to ever be up-to-date.
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PHONY_NOTMAIN = afterdepend afterinstall all beforedepend beforeinstall \
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beforelinking build build-tools buildfiles buildincludes \
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checkdpadd clean cleandepend cleandir cleanobj configure \
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depend dependall distclean distribute exe \
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html includes install installfiles installincludes lint \
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obj objlink objs objwarn realall realdepend \
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realinstall regress subdir-all subdir-depend subdir-install \
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tags whereobj
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.PHONY: ${PHONY_NOTMAIN}
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.NOTMAIN: ${PHONY_NOTMAIN}
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CSTD= c99
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.if ${CSTD} == "k&r"
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CFLAGS+= -traditional
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.elif ${CSTD} == "c89" || ${CSTD} == "c90"
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CFLAGS+= -std=iso9899:1990
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.elif ${CSTD} == "c94" || ${CSTD} == "c95"
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CFLAGS+= -std=iso9899:199409
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.elif ${CSTD} == "c99"
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CFLAGS+= -std=iso9899:1999
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.else # CSTD
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CFLAGS+= -std=${CSTD}
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.endif # CSTD
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