8dfc7699a6
reverse order to easily support variadic arguments. Thus, instead of using the proper stdarg.h macros (that nowadays are compiler-dependent), it may be tempting to directly take the address of the last argument and considering it as the start of an array. This is a shortcut that avoid looping to get all the arguments as the CPU already pushed them on the stack before the call to the function. Unfortunately, such an assumption is strictly compiler-dependent and compilers are free to move the last argument on the stack, as a local variable, and return the address of the location where the argument was stored, if asked for. This will break things as the rest of the array's argument are stored elsewhere (typically, a couple of words above the location where the argument was stored). This patch fixes the issue by allowing ACK to take the shortcut and enabling gcc/llvm-gcc to follow the right way.
49 lines
2 KiB
C
49 lines
2 KiB
C
/* Definitions for compiler-specific features. */
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#ifndef _MINIX_COMPILER_H
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#define _MINIX_COMPILER_H
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/*===========================================================================*
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* Compiler overrides *
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*===========================================================================*/
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/* ACK */
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#ifdef __ACK__
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#include <minix/compiler-ack.h>
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#endif
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/*===========================================================================*
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* Default values *
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*===========================================================================*/
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/*
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* cdecl calling convention expects the callee to pop the hidden pointer on
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* struct return. For example, GCC and LLVM comply with this (tested on IA32).
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*/
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#ifndef BYTES_TO_POP_ON_STRUCT_RETURN
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#define BYTES_TO_POP_ON_STRUCT_RETURN $4
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#endif
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/*
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* cdecl calling convention requires to push arguments on the stack in a
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* reverse order to easily support variadic arguments. Thus, instead of
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* using the proper stdarg.h macros (that nowadays are
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* compiler-dependant), it may be tempting to directly take the address of
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* the last argument and considering it as the start of an array. This is
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* a shortcut that avoid looping to get all the arguments as the CPU
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* already pushed them on the stack before the call to the function.
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*
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* Unfortunately, such an assumption is strictly compiler-dependant and
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* compilers are free to move the last argument on the stack, as a local
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* variable, and return the address of the location where the argument was
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* stored, if asked for. This will break things as the rest of the array's
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* argument are stored elsewhere (typically, a couple of words above the
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* location where the argument was stored).
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*
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* Conclusion: if unsure on what the compiler may do, do not make any
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* assumption and use the right (typically compiler-dependant) macros.
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*/
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#ifndef FUNC_ARGS_ARRAY
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#define FUNC_ARGS_ARRAY 0
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#endif
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#endif /* _MINIX_COMPILER_H */
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