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// https://gcc.gnu.org/onlinedocs/gcc-10.1.0/gcc/Common-Function-Attributes.html
access
access (access-mode, ref-index)
access (access-mode, ref-index, size-index)
// примеры:
__attribute__ ((access (read_only, 1))) int puts (const char*);
__attribute__ ((access (read_only, 1, 2))) void* memcpy (void*, const void*, size_t);
__attribute__ ((access (read_write, 1), access (read_only, 2))) char* strcat (char*, const char*);
__attribute__ ((access (write_only, 1), access (read_only, 2))) char* strcpy (char*, const char*);
__attribute__ ((access (write_only, 1, 2), access (read_write, 3))) int fgets (char*, int, FILE*);
В GCC 10 какой-то новый атрибут access появился, чтоб более строго что-то там гарантировать:
The access attribute enables the detection of invalid or unsafe accesses by functions to which they apply or their callers, as well as write-only accesses to objects that are never read from. Such accesses may be diagnosed by warnings such as -Wstringop-overflow, -Wuninitialized, -Wunused, and others.
The access attribute specifies that a function to whose by-reference arguments the attribute applies accesses the referenced object according to access-mode. The access-mode argument is required and must be one of three names: read_only, read_write, or write_only. The remaining two are positional arguments.
The required ref-index positional argument denotes a function argument of pointer (or in C++, reference) type that is subject to the access. The same pointer argument can be referenced by at most one distinct access attribute.
The optional size-index positional argument denotes a function argument of integer type that specifies the maximum size of the access. The size is the number of elements of the type referenced by ref-index, or the number of bytes when the pointer type is void*. When no size-index argument is specified, the pointer argument must be either null or point to a space that is suitably aligned and large for at least one object of the referenced type (this implies that a past-the-end pointer is not a valid argument). The actual size of the access may be less but it must not be more.
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