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When building with `make DEVELOPER=1` we explicitly pass "-std=gnu99" to
the compiler so that we don't start leaning on features exposed by more
recent versions of the C standard. Unfortunately though, glibc 2.43
started to use type-generic expressions. This works alright with GCC,
but when compiling with Clang this leads to errors:
$ make DEVELOPER=1 CC=clang
CC daemon.o
In file included from daemon.c:3:
./git-compat-util.h:344:11: error: '_Generic' is a C11 extension [-Werror,-Wc11-extensions]
344 | return !!strchr(path, '/');
| ^
/usr/include/string.h:265:3: note: expanded from macro 'strchr'
265 | __glibc_const_generic (S, const char *, strchr (S, C))
| ^
/usr/include/x86_64-linux-gnu/sys/cdefs.h:838:3: note: expanded from macro '__glibc_const_generic'
838 | _Generic (0 ? (PTR) : (void *) 1, \
| ^
In theory, the `__glibc_const_generic` macro does have feature gating:
#if !defined __cplusplus \
&& (__GNUC_PREREQ (4, 9) \
|| __glibc_has_extension (c_generic_selections) \
|| (!defined __GNUC__ && defined __STDC_VERSION__ \
&& __STDC_VERSION__ >= 201112L))
# define __HAVE_GENERIC_SELECTION 1
#else
# define __HAVE_GENERIC_SELECTION 0
#endif
But this feature gating isn't effective because `_has_extension()` will
always evaluate to true as C generics _are_ available as a language
extension to GNU C99 when using Clang. This would have been different if
`_has_feature()` was used instead, in which case it would have properly
evaluated to `false`.
GCC has a workaround to squelch this warning from standard system
headers, but because clang fails due to [-Werror,-Wc11-extensions],
as it lacks the corresponding workaround.
For both meson and Makefile, pass -Wno-c11-extensions when we are
building with clang.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Helped-by: Shardul Natu <snatu@google.com>
[jc: replaced Makefile side with Shardul's approach]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
114 lines
3.7 KiB
Plaintext
114 lines
3.7 KiB
Plaintext
ifndef COMPILER_FEATURES
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COMPILER_FEATURES := $(shell ./detect-compiler $(CC))
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endif
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ifeq ($(filter no-error,$(DEVOPTS)),)
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DEVELOPER_CFLAGS += -Werror
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SPARSE_FLAGS += -Wsparse-error
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endif
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DEVELOPER_CFLAGS += -Wall
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ifeq ($(filter no-pedantic,$(DEVOPTS)),)
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DEVELOPER_CFLAGS += -pedantic
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ifneq ($(or $(filter gcc5,$(COMPILER_FEATURES)),$(filter clang4,$(COMPILER_FEATURES))),)
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DEVELOPER_CFLAGS += -Wpedantic
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ifneq ($(filter gcc10,$(COMPILER_FEATURES)),)
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ifeq ($(uname_S),MINGW)
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DEVELOPER_CFLAGS += -Wno-pedantic-ms-format
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endif
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endif
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endif
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endif
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ifneq ($(uname_S),FreeBSD)
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ifneq ($(or $(filter gcc6,$(COMPILER_FEATURES)),$(filter clang7,$(COMPILER_FEATURES))),)
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DEVELOPER_CFLAGS += -std=gnu99
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endif
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else
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# FreeBSD cannot limit to C99 because its system headers unconditionally
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# rely on C11 features.
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endif
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DEVELOPER_CFLAGS += -Wdeclaration-after-statement
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DEVELOPER_CFLAGS += -Wformat-security
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DEVELOPER_CFLAGS += -Wold-style-definition
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DEVELOPER_CFLAGS += -Woverflow
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DEVELOPER_CFLAGS += -Wpointer-arith
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DEVELOPER_CFLAGS += -Wstrict-prototypes
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DEVELOPER_CFLAGS += -Wunused
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DEVELOPER_CFLAGS += -Wvla
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DEVELOPER_CFLAGS += -Wwrite-strings
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DEVELOPER_CFLAGS += -fno-common
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DEVELOPER_CFLAGS += -Wunreachable-code
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ifneq ($(filter clang9,$(COMPILER_FEATURES)),)
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DEVELOPER_CFLAGS += -Wcomma
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endif
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ifneq ($(filter clang4,$(COMPILER_FEATURES)),)
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DEVELOPER_CFLAGS += -Wtautological-constant-out-of-range-compare
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endif
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ifneq ($(or $(filter gcc6,$(COMPILER_FEATURES)),$(filter clang4,$(COMPILER_FEATURES))),)
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DEVELOPER_CFLAGS += -Wextra
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# if a function is public, there should be a prototype and the right
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# header file should be included. If not, it should be static.
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DEVELOPER_CFLAGS += -Wmissing-prototypes
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ifeq ($(filter extra-all,$(DEVOPTS)),)
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# These are disabled because we have these all over the place.
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DEVELOPER_CFLAGS += -Wno-empty-body
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DEVELOPER_CFLAGS += -Wno-missing-field-initializers
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endif
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endif
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# uninitialized warnings on gcc 4.9.2 in xdiff/xdiffi.c and config.c
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# not worth fixing since newer compilers correctly stop complaining
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#
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# Likewise, gcc older than 4.9 complains about initializing a
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# struct-within-a-struct using just "{ 0 }"
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ifneq ($(filter gcc4,$(COMPILER_FEATURES)),)
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ifeq ($(filter gcc5,$(COMPILER_FEATURES)),)
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DEVELOPER_CFLAGS += -Wno-uninitialized
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DEVELOPER_CFLAGS += -Wno-missing-braces
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endif
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endif
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# Old versions of clang complain about initializing a
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# struct-within-a-struct using just "{0}" rather than "{{0}}". This
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# error is considered a false-positive and not worth fixing, because
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# new clang versions do not, so just disable it.
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#
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# The "bug" was fixed in upstream clang 9.
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#
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# Complicating this is that versions of clang released by Apple have
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# their own version numbers (associated with the corresponding version
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# of XCode) unrelated to the official clang version numbers.
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#
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# The bug was fixed in Apple clang 12.
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#
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ifneq ($(filter clang1,$(COMPILER_FEATURES)),) # if we are using clang
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ifeq ($(uname_S),Darwin) # if we are on darwin
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ifeq ($(filter clang12,$(COMPILER_FEATURES)),) # if version < 12
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DEVELOPER_CFLAGS += -Wno-missing-braces
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endif
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else # not darwin
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ifeq ($(filter clang9,$(COMPILER_FEATURES)),) # if version < 9
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DEVELOPER_CFLAGS += -Wno-missing-braces
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endif
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endif
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endif
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# glibc 2.43 headers unconditionally use _Generic even when we ask the
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# compiler to stick to -std=gnu99 and unlike GCC, clang lacks a
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# workaround to squelch warnings from system headers.
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ifneq ($(filter clang1,$(COMPILER_FEATURES)),) # if we are using clang
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DEVELOPER_CFLAGS += -Wno-c11-extensions
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endif
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# https://bugzilla.redhat.com/show_bug.cgi?id=2075786
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ifneq ($(filter gcc12,$(COMPILER_FEATURES)),)
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DEVELOPER_CFLAGS += -Wno-error=stringop-overread
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endif
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GIT_TEST_PERL_FATAL_WARNINGS = YesPlease
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