d3584b4a46
`extern "C"` is not a valid language linkage for declaring `int main(...)`, as per the ISO C++ Standard Specification. This fixes the violations of -Wmain, and brings Zephyr closer to valid C++. See the C++ standard wording here: https://eel.is/c++draft/basic.start.main#3.sentence-5 See also the clang warning -Wmain: https://clang.llvm.org/docs/DiagnosticsReference.html#wmain However, for freestanding code (i.e. with -ffreestanding), main has no special meaning, and we need to prevent name mangling. So allow this forward linkage when not hosted. This only applies to C++ as these linkage declarations only exist inside __cplusplus guards. Signed-off-by: Jordan R Abrahams-Whitehead <ajordanr@google.com>
74 lines
2.3 KiB
C
74 lines
2.3 KiB
C
/*
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* Copyright (c) 2017 Linaro Limited
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef ZEPHYR_INCLUDE_ZEPHYR_TYPES_H_
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#define ZEPHYR_INCLUDE_ZEPHYR_TYPES_H_
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#include <stddef.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* A type with strong alignment requirements, similar to C11 max_align_t. It can
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* be used to force alignment of data structures allocated on the stack or as
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* return * type for heap allocators.
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*/
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typedef union {
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long long thelonglong;
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long double thelongdouble;
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uintmax_t theuintmax_t;
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size_t thesize_t;
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uintptr_t theuintptr_t;
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void *thepvoid;
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void (*thepfunc)(void);
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} z_max_align_t;
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/*
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* Thread local variables are declared with different keywords depending on
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* which C/C++ standard that is used. C++11 and C23 uses "thread_local" whilst
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* C11 uses "_Thread_local". Previously the GNU "__thread" keyword was used
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* which is the same in both gcc and g++.
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*/
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#ifndef Z_THREAD_LOCAL
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#if defined(__cplusplus) && (__cplusplus) >= 201103L /* C++11 */
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#define Z_THREAD_LOCAL thread_local
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#elif defined(__STDC_VERSION__) && (__STDC_VERSION__) >= 202311L /* C23 */
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#define Z_THREAD_LOCAL thread_local
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#elif defined(__STDC_VERSION__) && (__STDC_VERSION__) >= 201112L /* C11 */
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#define Z_THREAD_LOCAL _Thread_local
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#else /* Default back to old behavior which used the GNU keyword. */
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#define Z_THREAD_LOCAL __thread
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#endif
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#endif /* Z_THREAD_LOCAL */
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#ifdef __cplusplus
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#if (!__STDC_HOSTED__)
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/*
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* Zephyr requires an int main(void) signature with C linkage for the
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* application main if present. gcc, and clang when building in 'hosted' mode
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* will correctly assume this. But, when building freestanding, clang does not
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* treat main() specially, and by default name mangles its symbol, which
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* results in the linker not linking from the kernel init code into this
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* name mangled app main().
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*
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* At the same time, according to the C++ standard Section 6.9.3.1 of
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* ISO/IEC 14882:2024, main cannot be explicitly declared to have "C" linkage.
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* This restriction is relaxed for freestanding code, as main is not treated
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* specially in these circumstances.
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* Therefore, let's include the prototype when we are not building the code as
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* freestanding/not-hosted.
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*/
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extern int main(void);
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#endif
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}
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#endif
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#endif /* ZEPHYR_INCLUDE_ZEPHYR_TYPES_H_ */
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