Fix -Wmaybe uninitialized

[andrewvoznytsa]

This little tweak fixes clang's "unknown warning group -Wmaybe-uninitialized".

[eyalroz]

I don't know that there's a maybe-uninitialized variable used in the code... where exactly?

[andrewvoznytsa]

No idea. From my perspective the problem is that the code assumes that it is compiled by gcc and with -Wmaybe-uninitialized support which is not always the case (clang-16 does not support such option, for example). This PR brings potential solution for this problem. If there is no real need in -Wmaybe-uninitialized then it should be removed and this PR dropped.

[eyalroz]

Oh, ok, now I see what you mean. However - the code builds just fine with clang 16.0.6. Can you paste the exact error output that you're getting?

[andrewvoznytsa]

Here it is:

clang -MMD -MF obj/third_party/printf/printf/printf.o.d -DPRINTF_SUPPORT_HUMAN_STYLE_SPECIFIERS -D_DEBUG -I../third_party/printf/src/src -fno-strict-aliasing -funwind-tables -fPIC --gcc-toolchain=../../../../../usr -fcolor-diagnostics --target=x86_64-linux-gnu -fstack-protector-strong -pthread -O0 -fno-omit-frame-pointer -gdwarf-3 -g2 -fvisibility=hidden -c ../third_party/printf/src/src/printf/printf.c -o obj/third_party/printf/printf/printf.o ../third_party/printf/src/src/printf/printf.c:942:32: warning: unknown warning group '-Wmaybe-uninitialized', ignored [-Wunknown-warning-option]

pragma GCC diagnostic ignored "-Wmaybe-uninitialized"

[andrewvoznytsa]

clang -v clang version 16.0.6 Target: x86_64-unknown-linux-gnu

[andrewvoznytsa]

And this one

clang -dM -E - < /dev/null

define _LP64 1

define __ATOMIC_ACQUIRE 2

define __ATOMIC_ACQ_REL 4

define __ATOMIC_CONSUME 1

define __ATOMIC_RELAXED 0

define __ATOMIC_RELEASE 3

define __ATOMIC_SEQ_CST 5

define __BIGGEST_ALIGNMENT__ 16

define __BITINT_MAXWIDTH__ 8388608

define __BOOL_WIDTH__ 8

define __BYTE_ORDER ORDER_LITTLE_ENDIAN__

define __CHAR16_TYPE__ unsigned short

define __CHAR32_TYPE__ unsigned int

define __CHAR_BIT__ 8

define __CLANG_ATOMIC_BOOL_LOCK_FREE 2

define __CLANG_ATOMIC_CHAR16_T_LOCK_FREE 2

define __CLANG_ATOMIC_CHAR32_T_LOCK_FREE 2

define __CLANG_ATOMIC_CHAR_LOCK_FREE 2

define __CLANG_ATOMIC_INT_LOCK_FREE 2

define __CLANG_ATOMIC_LLONG_LOCK_FREE 2

define __CLANG_ATOMIC_LONG_LOCK_FREE 2

define __CLANG_ATOMIC_POINTER_LOCK_FREE 2

define __CLANG_ATOMIC_SHORT_LOCK_FREE 2

define __CLANG_ATOMIC_WCHAR_T_LOCK_FREE 2

define __CONSTANT_CFSTRINGS__ 1

define DBL_DECIMAL_DIG 17

define DBL_DENORM_MIN 4.9406564584124654e-324

define __DBL_DIG__ 15

define __DBL_EPSILON__ 2.2204460492503131e-16

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__ 1.7976931348623157e+308

define __DBL_MIN_10_EXP__ (-307)

define DBL_MIN_EXP (-1021)

define __DBL_MIN__ 2.2250738585072014e-308

define __DECIMAL_DIG LDBL_DECIMAL_DIG__

define ELF 1

define FINITE_MATH_ONLY 0

define FLOAT128 1

define FLT16_DECIMAL_DIG 5

define FLT16_DENORM_MIN 5.9604644775390625e-8F16

define __FLT16_DIG__ 3

define __FLT16_EPSILON__ 9.765625e-4F16

define FLT16_HAS_DENORM 1

define FLT16_HAS_INFINITY 1

define __FLT16_HAS_QUIET_NAN__ 1

define FLT16_MANT_DIG 11

define __FLT16_MAX_10_EXP__ 4

define FLT16_MAX_EXP 16

define __FLT16_MAX__ 6.5504e+4F16

define __FLT16_MIN_10_EXP__ (-4)

define FLT16_MIN_EXP (-13)

define __FLT16_MIN__ 6.103515625e-5F16

define FLT_DECIMAL_DIG 9

define FLT_DENORM_MIN 1.40129846e-45F

define __FLT_DIG__ 6

define __FLT_EPSILON__ 1.19209290e-7F

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__ 3.40282347e+38F

define __FLT_MIN_10_EXP__ (-37)

define FLT_MIN_EXP (-125)

define __FLT_MIN__ 1.17549435e-38F

define __FLT_RADIX__ 2

define FXSR 1

define __GCC_ASM_FLAG_OUTPUTS__ 1

define __GCC_ATOMIC_BOOL_LOCK_FREE 2

define __GCC_ATOMIC_CHAR16_T_LOCK_FREE 2

define __GCC_ATOMIC_CHAR32_T_LOCK_FREE 2

define __GCC_ATOMIC_CHAR_LOCK_FREE 2

define __GCC_ATOMIC_INT_LOCK_FREE 2

define __GCC_ATOMIC_LLONG_LOCK_FREE 2

define __GCC_ATOMIC_LONG_LOCK_FREE 2

define __GCC_ATOMIC_POINTER_LOCK_FREE 2

define __GCC_ATOMIC_SHORT_LOCK_FREE 2

define __GCC_ATOMIC_TEST_AND_SET_TRUEVAL 1

define __GCC_ATOMIC_WCHAR_T_LOCK_FREE 2

define __GCC_HAVE_DWARF2_CFI_ASM 1

define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1

define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1

define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1

define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1

define __GNUC_MINOR__ 2

define __GNUC_PATCHLEVEL__ 1

define GNUC_STDC_INLINE 1

define GNUC 4

define __GXX_ABI_VERSION 1002

define INT16_C_SUFFIX

define __INT16_FMTd__ "hd"

define __INT16_FMTi__ "hi"

define __INT16_MAX__ 32767

define __INT16_TYPE__ short

define INT32_C_SUFFIX

define __INT32_FMTd__ "d"

define __INT32_FMTi__ "i"

define __INT32_MAX__ 2147483647

define __INT32_TYPE__ int

define INT64_C_SUFFIX L

define __INT64_FMTd__ "ld"

define __INT64_FMTi__ "li"

define __INT64_MAX__ 9223372036854775807L

define __INT64_TYPE__ long int

define INT8_C_SUFFIX

define __INT8_FMTd__ "hhd"

define __INT8_FMTi__ "hhi"

define __INT8_MAX__ 127

define __INT8_TYPE__ signed char

define INTMAX_C_SUFFIX L

define __INTMAX_FMTd__ "ld"

define __INTMAX_FMTi__ "li"

define __INTMAX_MAX__ 9223372036854775807L

define __INTMAX_TYPE__ long int

define __INTMAX_WIDTH__ 64

define __INTPTR_FMTd__ "ld"

define __INTPTR_FMTi__ "li"

define __INTPTR_MAX__ 9223372036854775807L

define __INTPTR_TYPE__ long int

define __INTPTR_WIDTH__ 64

define INT_FAST16_FMTd "hd"

define INT_FAST16_FMTi "hi"

define INT_FAST16_MAX 32767

define INT_FAST16_TYPE short

define INT_FAST16_WIDTH 16

define INT_FAST32_FMTd "d"

define INT_FAST32_FMTi "i"

define INT_FAST32_MAX 2147483647

define INT_FAST32_TYPE int

define INT_FAST32_WIDTH 32

define INT_FAST64_FMTd "ld"

define INT_FAST64_FMTi "li"

define INT_FAST64_MAX 9223372036854775807L

define INT_FAST64_TYPE long int

define INT_FAST64_WIDTH 64

define INT_FAST8_FMTd "hhd"

define INT_FAST8_FMTi "hhi"

define INT_FAST8_MAX 127

define INT_FAST8_TYPE signed char

define INT_FAST8_WIDTH 8

define INT_LEAST16_FMTd "hd"

define INT_LEAST16_FMTi "hi"

define INT_LEAST16_MAX 32767

define INT_LEAST16_TYPE short

define INT_LEAST16_WIDTH 16

define INT_LEAST32_FMTd "d"

define INT_LEAST32_FMTi "i"

define INT_LEAST32_MAX 2147483647

define INT_LEAST32_TYPE int

define INT_LEAST32_WIDTH 32

define INT_LEAST64_FMTd "ld"

define INT_LEAST64_FMTi "li"

define INT_LEAST64_MAX 9223372036854775807L

define INT_LEAST64_TYPE long int

define INT_LEAST64_WIDTH 64

define INT_LEAST8_FMTd "hhd"

define INT_LEAST8_FMTi "hhi"

define INT_LEAST8_MAX 127

define INT_LEAST8_TYPE signed char

define INT_LEAST8_WIDTH 8

define __INT_MAX__ 2147483647

define __INT_WIDTH__ 32

define LDBL_DECIMAL_DIG 21

define LDBL_DENORM_MIN 3.64519953188247460253e-4951L

define __LDBL_DIG__ 18

define __LDBL_EPSILON__ 1.08420217248550443401e-19L

define LDBL_HAS_DENORM 1

define LDBL_HAS_INFINITY 1

define __LDBL_HAS_QUIET_NAN__ 1

define LDBL_MANT_DIG 64

define __LDBL_MAX_10_EXP__ 4932

define LDBL_MAX_EXP 16384

define __LDBL_MAX__ 1.18973149535723176502e+4932L

define __LDBL_MIN_10_EXP__ (-4931)

define LDBL_MIN_EXP (-16381)

define __LDBL_MIN__ 3.36210314311209350626e-4932L

define __LITTLE_ENDIAN__ 1

define __LLONG_WIDTH__ 64

define LONG_LONG_MAX 9223372036854775807LL

define __LONG_MAX__ 9223372036854775807L

define __LONG_WIDTH__ 64

define LP64 1

define MMX 1

define __NO_INLINE__ 1

define __NO_MATH_INLINES 1

define __OBJC_BOOL_IS_BOOL 0

define __OPENCL_MEMORY_SCOPE_ALL_SVM_DEVICES 3

define __OPENCL_MEMORY_SCOPE_DEVICE 2

define __OPENCL_MEMORY_SCOPE_SUB_GROUP 4

define __OPENCL_MEMORY_SCOPE_WORK_GROUP 1

define __OPENCL_MEMORY_SCOPE_WORK_ITEM 0

define ORDER_BIG_ENDIAN 4321

define ORDER_LITTLE_ENDIAN 1234

define ORDER_PDP_ENDIAN 3412

define PIC 2

define PIE 2

define __POINTER_WIDTH__ 64

define __PRAGMA_REDEFINE_EXTNAME 1

define __PTRDIFF_FMTd__ "ld"

define __PTRDIFF_FMTi__ "li"

define __PTRDIFF_MAX__ 9223372036854775807L

define __PTRDIFF_TYPE__ long int

define __PTRDIFF_WIDTH__ 64

define __REGISTER_PREFIX__

define __SCHAR_MAX__ 127

define __SEG_FS 1

define __SEG_GS 1

define __SHRT_MAX__ 32767

define __SHRT_WIDTH__ 16

define SIG_ATOMIC_MAX 2147483647

define SIG_ATOMIC_WIDTH 32

define __SIZEOF_DOUBLE__ 8

define __SIZEOF_FLOAT128__ 16

define __SIZEOF_FLOAT__ 4

define __SIZEOF_INT128__ 16

define __SIZEOF_INT__ 4

define SIZEOF_LONG_DOUBLE 16

define SIZEOF_LONG_LONG 8

define __SIZEOF_LONG__ 8

define __SIZEOF_POINTER__ 8

define SIZEOF_PTRDIFF_T 8

define __SIZEOF_SHORT__ 2

define SIZEOF_SIZE_T 8

define SIZEOF_WCHAR_T 4

define SIZEOF_WINT_T 4

define __SIZE_FMTX__ "lX"

define __SIZE_FMTo__ "lo"

define __SIZE_FMTu__ "lu"

define __SIZE_FMTx__ "lx"

define __SIZE_MAX__ 18446744073709551615UL

define __SIZE_TYPE__ long unsigned int

define __SIZE_WIDTH__ 64

define __SSE2_MATH__ 1

define SSE2 1

define __SSE_MATH__ 1

define SSE 1

define __STDC_HOSTED__ 1

define STDC_UTF_16 1

define STDC_UTF_32 1

define __STDC_VERSION__ 201710L

define STDC 1

define UINT16_C_SUFFIX

define __UINT16_FMTX__ "hX"

define __UINT16_FMTo__ "ho"

define __UINT16_FMTu__ "hu"

define __UINT16_FMTx__ "hx"

define __UINT16_MAX__ 65535

define __UINT16_TYPE__ unsigned short

define UINT32_C_SUFFIX U

define __UINT32_FMTX__ "X"

define __UINT32_FMTo__ "o"

define __UINT32_FMTu__ "u"

define __UINT32_FMTx__ "x"

define __UINT32_MAX__ 4294967295U

define __UINT32_TYPE__ unsigned int

define UINT64_C_SUFFIX UL

define __UINT64_FMTX__ "lX"

define __UINT64_FMTo__ "lo"

define __UINT64_FMTu__ "lu"

define __UINT64_FMTx__ "lx"

define __UINT64_MAX__ 18446744073709551615UL

define __UINT64_TYPE__ long unsigned int

define UINT8_C_SUFFIX

define __UINT8_FMTX__ "hhX"

define __UINT8_FMTo__ "hho"

define __UINT8_FMTu__ "hhu"

define __UINT8_FMTx__ "hhx"

define __UINT8_MAX__ 255

define __UINT8_TYPE__ unsigned char

define UINTMAX_C_SUFFIX UL

define __UINTMAX_FMTX__ "lX"

define __UINTMAX_FMTo__ "lo"

define __UINTMAX_FMTu__ "lu"

define __UINTMAX_FMTx__ "lx"

define __UINTMAX_MAX__ 18446744073709551615UL

define __UINTMAX_TYPE__ long unsigned int

define __UINTMAX_WIDTH__ 64

define __UINTPTR_FMTX__ "lX"

define __UINTPTR_FMTo__ "lo"

define __UINTPTR_FMTu__ "lu"

define __UINTPTR_FMTx__ "lx"

define __UINTPTR_MAX__ 18446744073709551615UL

define __UINTPTR_TYPE__ long unsigned int

define __UINTPTR_WIDTH__ 64

define UINT_FAST16_FMTX "hX"

define UINT_FAST16_FMTo "ho"

define UINT_FAST16_FMTu "hu"

define UINT_FAST16_FMTx "hx"

define UINT_FAST16_MAX 65535

define UINT_FAST16_TYPE unsigned short

define UINT_FAST32_FMTX "X"

define UINT_FAST32_FMTo "o"

define UINT_FAST32_FMTu "u"

define UINT_FAST32_FMTx "x"

define UINT_FAST32_MAX 4294967295U

define UINT_FAST32_TYPE unsigned int

define UINT_FAST64_FMTX "lX"

define UINT_FAST64_FMTo "lo"

define UINT_FAST64_FMTu "lu"

define UINT_FAST64_FMTx "lx"

define UINT_FAST64_MAX 18446744073709551615UL

define UINT_FAST64_TYPE long unsigned int

define UINT_FAST8_FMTX "hhX"

define UINT_FAST8_FMTo "hho"

define UINT_FAST8_FMTu "hhu"

define UINT_FAST8_FMTx "hhx"

define UINT_FAST8_MAX 255

define UINT_FAST8_TYPE unsigned char

define UINT_LEAST16_FMTX "hX"

define UINT_LEAST16_FMTo "ho"

define UINT_LEAST16_FMTu "hu"

define UINT_LEAST16_FMTx "hx"

define UINT_LEAST16_MAX 65535

define UINT_LEAST16_TYPE unsigned short

define UINT_LEAST32_FMTX "X"

define UINT_LEAST32_FMTo "o"

define UINT_LEAST32_FMTu "u"

define UINT_LEAST32_FMTx "x"

define UINT_LEAST32_MAX 4294967295U

define UINT_LEAST32_TYPE unsigned int

define UINT_LEAST64_FMTX "lX"

define UINT_LEAST64_FMTo "lo"

define UINT_LEAST64_FMTu "lu"

define UINT_LEAST64_FMTx "lx"

define UINT_LEAST64_MAX 18446744073709551615UL

define UINT_LEAST64_TYPE long unsigned int

define UINT_LEAST8_FMTX "hhX"

define UINT_LEAST8_FMTo "hho"

define UINT_LEAST8_FMTu "hhu"

define UINT_LEAST8_FMTx "hhx"

define UINT_LEAST8_MAX 255

define UINT_LEAST8_TYPE unsigned char

define USER_LABEL_PREFIX

define VERSION "Clang 16.0.6"

define __WCHAR_MAX__ 2147483647

define __WCHAR_TYPE__ int

define __WCHAR_WIDTH__ 32

define __WINT_MAX__ 4294967295U

define __WINT_TYPE__ unsigned int

define __WINT_UNSIGNED__ 1

define __WINT_WIDTH__ 32

define __amd64 1

define amd64 1

define clang 1

define clang_literal_encoding "UTF-8"

define __clang_major__ 16

define __clang_minor__ 0

define __clang_patchlevel__ 6

define __clang_version__ "16.0.6 "

define __clang_wide_literal_encoding__ "UTF-32"

define code_model_small 1

define __gnu_linux__ 1

define __k8 1

define k8 1

define __linux 1

define linux 1

define llvm 1

define pic 2

define pie 2

define __seg_fs attribute((address_space(257)))

define __seg_gs attribute((address_space(256)))

define __tune_k8__ 1

define __unix 1

define unix 1

define __x86_64 1

define __x86_64__ 1

define linux 1

define unix 1

[eyalroz]

Ah, well, you were getting this warning because you weren't building it the way I suggested, which does have these warnings turned on. I can reproduce this now with just clang -I src/ -c src/printf/printf.c -o printf.o in the repository root dir.

Anyway, it can't hurt I guess, so - will accept this. Would have liked an issue filed first though.

[eyalroz]

Ah, well, this breaks the build:

[ 12%] Building C object CMakeFiles/printf.dir/src/printf/printf.c.o
/home/runner/work/printf/printf/src/printf/printf.c: In function ‘unapply_scaling’:
/home/runner/work/printf/printf/src/printf/printf.c:659:45: error: missing binary operator before token "("
  659 | #if !defined(__has_warning) || __has_warning("-Wmaybe-uninitialized")
      |                                             ^
/home/runner/work/printf/printf/src/printf/printf.c: In function ‘print_exponential_number’:
/home/runner/work/printf/printf/src/printf/printf.c:941:45: error: missing binary operator before token "("
  941 | #if !defined(__has_warning) || __has_warning("-Wmaybe-uninitialized")
      |                                             ^

so we have to try something more complex.

[andrewvoznytsa]

Then I'll look for something better.

[eyalroz]

Just look at what I've committed, i.e. pull the HEAD of develop. Tell me if that works for you.

[andrewvoznytsa]

Yes, that works perfectly - thank you!

[eyalroz]

... and I have now made a beta release of a new version with this and a few additional fixes.

[andrewvoznytsa]

:+1: Next time if I decide to submit something I'll start with an issue - finally managed to read your README ;-)