How to detect compilation by Android NDK in a C/C++ file?
It is #ifdef __ANDROID__ as seen by running the preprocessor:
~$ /usr/local/android-ndk-r6/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin/arm-linux-androideabi-gcc -E -dM - < /dev/null | grep -i android
The output is:
#define __ANDROID__ 1
No need to depend on defining stuff in your project especially if you're skipping the NDK build system.
Short answer: #ifdef ANDROID .
The ANDROID macro is defined for you in build-module.mk (part of the standard build system):
# always define ANDROID when building binaries
#
LOCAL_CFLAGS := -DANDROID $(LOCAL_CFLAGS)
This is a late answer, but for completeness, here are the preprocessor definitions for android-eabi before including any header files. A C++ header will bring in a slew of additional headers.
The output below is from Detecting Android in C/C++ Source Files (Preprocessor Macros) (circa 2013) on the Android NDK mailing list. Notice __ANDROID__ is defined, but not __android__ or ANDROID.
$ arm-linux-androideabi-cpp -dM < /dev/null | sort
#define __ANDROID__ 1
#define __APCS_32__ 1
#define __ARMEL__ 1
#define __ARM_ARCH_5TE__ 1
#define __ARM_EABI__ 1
#define __ARM_FEATURE_DSP 1
#define __ARM_PCS 1
#define __BIGGEST_ALIGNMENT__ 8
#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __CHAR16_TYPE__ short unsigned int
#define __CHAR32_TYPE__ unsigned int
#define __CHAR_BIT__ 8
#define __CHAR_UNSIGNED__ 1
#define __DBL_DECIMAL_DIG__ 17
#define __DBL_DENORM_MIN__ ((double)4.9406564584124654e-324L)
#define __DBL_DIG__ 15
#define __DBL_EPSILON__ ((double)2.2204460492503131e-16L)
#define __DBL_HAS_DENORM__ 1
#define __DBL_HAS_INFINITY__ 1
#define __DBL_HAS_QUIET_NAN__ 1
#define __DBL_MANT_DIG__ 53
#define __DBL_MAX_10_EXP__ 308
#define __DBL_MAX_EXP__ 1024
#define __DBL_MAX__ ((double)1.7976931348623157e+308L)
#define __DBL_MIN_10_EXP__ (-307)
#define __DBL_MIN_EXP__ (-1021)
#define __DBL_MIN__ ((double)2.2250738585072014e-308L)
#define __DEC128_EPSILON__ 1E-33DL
#define __DEC128_MANT_DIG__ 34
#define __DEC128_MAX_EXP__ 6145
#define __DEC128_MAX__ 9.999999999999999999999999999999999E6144DL
#define __DEC128_MIN_EXP__ (-6142)
#define __DEC128_MIN__ 1E-6143DL
#define __DEC128_SUBNORMAL_MIN__ 0.000000000000000000000000000000001E-6143DL
#define __DEC32_EPSILON__ 1E-6DF
#define __DEC32_MANT_DIG__ 7
#define __DEC32_MAX_EXP__ 97
#define __DEC32_MAX__ 9.999999E96DF
#define __DEC32_MIN_EXP__ (-94)
#define __DEC32_MIN__ 1E-95DF
#define __DEC32_SUBNORMAL_MIN__ 0.000001E-95DF
#define __DEC64_EPSILON__ 1E-15DD
#define __DEC64_MANT_DIG__ 16
#define __DEC64_MAX_EXP__ 385
#define __DEC64_MAX__ 9.999999999999999E384DD
#define __DEC64_MIN_EXP__ (-382)
#define __DEC64_MIN__ 1E-383DD
#define __DEC64_SUBNORMAL_MIN__ 0.000000000000001E-383DD
#define __DECIMAL_DIG__ 17
#define __DEC_EVAL_METHOD__ 2
#define __ELF__ 1
#define __FINITE_MATH_ONLY__ 0
#define __FLOAT_WORD_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __FLT_DECIMAL_DIG__ 9
#define __FLT_DENORM_MIN__ 1.4012984643248171e-45F
#define __FLT_DIG__ 6
#define __FLT_EPSILON__ 1.1920928955078125e-7F
#define __FLT_EVAL_METHOD__ 0
#define __FLT_HAS_DENORM__ 1
#define __FLT_HAS_INFINITY__ 1
#define __FLT_HAS_QUIET_NAN__ 1
#define __FLT_MANT_DIG__ 24
#define __FLT_MAX_10_EXP__ 38
#define __FLT_MAX_EXP__ 128
#define __FLT_MAX__ 3.4028234663852886e+38F
#define __FLT_MIN_10_EXP__ (-37)
#define __FLT_MIN_EXP__ (-125)
#define __FLT_MIN__ 1.1754943508222875e-38F
#define __FLT_RADIX__ 2
#define __GNUC_GNU_INLINE__ 1
#define __GNUC_MINOR__ 6
#define __GNUC_PATCHLEVEL__ 0
#define __GNUC__ 4
#define __GXX_ABI_VERSION 1002
#define __GXX_TYPEINFO_EQUALITY_INLINE 0
#define __INT16_C(c) c
#define __INT16_MAX__ 32767
#define __INT16_TYPE__ short int
#define __INT32_C(c) c
#define __INT32_MAX__ 2147483647
#define __INT32_TYPE__ int
#define __INT64_C(c) c ## LL
#define __INT64_MAX__ 9223372036854775807LL
#define __INT64_TYPE__ long long int
#define __INT8_C(c) c
#define __INT8_MAX__ 127
#define __INT8_TYPE__ signed char
#define __INTMAX_C(c) c ## LL
#define __INTMAX_MAX__ 9223372036854775807LL
#define __INTMAX_TYPE__ long long int
#define __INTPTR_MAX__ 2147483647
#define __INTPTR_TYPE__ int
#define __INT_FAST16_MAX__ 2147483647
#define __INT_FAST16_TYPE__ int
#define __INT_FAST32_MAX__ 2147483647
#define __INT_FAST32_TYPE__ int
#define __INT_FAST64_MAX__ 9223372036854775807LL
#define __INT_FAST64_TYPE__ long long int
#define __INT_FAST8_MAX__ 127
#define __INT_FAST8_TYPE__ signed char
#define __INT_LEAST16_MAX__ 32767
#define __INT_LEAST16_TYPE__ short int
#define __INT_LEAST32_MAX__ 2147483647
#define __INT_LEAST32_TYPE__ int
#define __INT_LEAST64_MAX__ 9223372036854775807LL
#define __INT_LEAST64_TYPE__ long long int
#define __INT_LEAST8_MAX__ 127
#define __INT_LEAST8_TYPE__ signed char
#define __INT_MAX__ 2147483647
#define __LDBL_DENORM_MIN__ 4.9406564584124654e-324L
#define __LDBL_DIG__ 15
#define __LDBL_EPSILON__ 2.2204460492503131e-16L
#define __LDBL_HAS_DENORM__ 1
#define __LDBL_HAS_INFINITY__ 1
#define __LDBL_HAS_QUIET_NAN__ 1
#define __LDBL_MANT_DIG__ 53
#define __LDBL_MAX_10_EXP__ 308
#define __LDBL_MAX_EXP__ 1024
#define __LDBL_MAX__ 1.7976931348623157e+308L
#define __LDBL_MIN_10_EXP__ (-307)
#define __LDBL_MIN_EXP__ (-1021)
#define __LDBL_MIN__ 2.2250738585072014e-308L
#define __LONG_LONG_MAX__ 9223372036854775807LL
#define __LONG_MAX__ 2147483647L
#define __NO_INLINE__ 1
#define __ORDER_BIG_ENDIAN__ 4321
#define __ORDER_LITTLE_ENDIAN__ 1234
#define __ORDER_PDP_ENDIAN__ 3412
#define __PIC__ 1
#define __PRAGMA_REDEFINE_EXTNAME 1
#define __PTRDIFF_MAX__ 2147483647
#define __PTRDIFF_TYPE__ int
#define __REGISTER_PREFIX__
#define __SCHAR_MAX__ 127
#define __SHRT_MAX__ 32767
#define __SIG_ATOMIC_MAX__ 2147483647
#define __SIG_ATOMIC_MIN__ (-__SIG_ATOMIC_MAX__ - 1)
#define __SIG_ATOMIC_TYPE__ int
#define __SIZEOF_DOUBLE__ 8
#define __SIZEOF_FLOAT__ 4
#define __SIZEOF_INT__ 4
#define __SIZEOF_LONG_DOUBLE__ 8
#define __SIZEOF_LONG_LONG__ 8
#define __SIZEOF_LONG__ 4
#define __SIZEOF_POINTER__ 4
#define __SIZEOF_PTRDIFF_T__ 4
#define __SIZEOF_SHORT__ 2
#define __SIZEOF_SIZE_T__ 4
#define __SIZEOF_WCHAR_T__ 4
#define __SIZEOF_WINT_T__ 4
#define __SIZE_MAX__ 4294967295U
#define __SIZE_TYPE__ unsigned int
#define __SOFTFP__ 1
#define __STDC_HOSTED__ 1
#define __STDC__ 1
#define __THUMB_INTERWORK__ 1
#define __UINT16_C(c) c
#define __UINT16_MAX__ 65535
#define __UINT16_TYPE__ short unsigned int
#define __UINT32_C(c) c ## U
#define __UINT32_MAX__ 4294967295U
#define __UINT32_TYPE__ unsigned int
#define __UINT64_C(c) c ## ULL
#define __UINT64_MAX__ 18446744073709551615ULL
#define __UINT64_TYPE__ long long unsigned int
#define __UINT8_C(c) c
#define __UINT8_MAX__ 255
#define __UINT8_TYPE__ unsigned char
#define __UINTMAX_C(c) c ## ULL
#define __UINTMAX_MAX__ 18446744073709551615ULL
#define __UINTMAX_TYPE__ long long unsigned int
#define __UINTPTR_MAX__ 4294967295U
#define __UINTPTR_TYPE__ unsigned int
#define __UINT_FAST16_MAX__ 4294967295U
#define __UINT_FAST16_TYPE__ unsigned int
#define __UINT_FAST32_MAX__ 4294967295U
#define __UINT_FAST32_TYPE__ unsigned int
#define __UINT_FAST64_MAX__ 18446744073709551615ULL
#define __UINT_FAST64_TYPE__ long long unsigned int
#define __UINT_FAST8_MAX__ 255
#define __UINT_FAST8_TYPE__ unsigned char
#define __UINT_LEAST16_MAX__ 65535
#define __UINT_LEAST16_TYPE__ short unsigned int
#define __UINT_LEAST32_MAX__ 4294967295U
#define __UINT_LEAST32_TYPE__ unsigned int
#define __UINT_LEAST64_MAX__ 18446744073709551615ULL
#define __UINT_LEAST64_TYPE__ long long unsigned int
#define __UINT_LEAST8_MAX__ 255
#define __UINT_LEAST8_TYPE__ unsigned char
#define __USER_LABEL_PREFIX__
#define __VERSION__ "4.6 20120106 (prerelease)"
#define __VFP_FP__ 1
#define __WCHAR_MAX__ 4294967295U
#define __WCHAR_MIN__ 0U
#define __WCHAR_TYPE__ unsigned int
#define __WINT_MAX__ 4294967295U
#define __WINT_MIN__ 0U
#define __WINT_TYPE__ unsigned int
#define __arm__ 1
#define __linux 1
#define __linux__ 1
#define __pic__ 1
#define __unix 1
#define __unix__ 1
#define linux 1
#define unix 1