Microchip Technology SW006023-2N Ficha De Dados
Functions
2012 Microchip Technology Inc.
DS51686E-page 131
Certain usages in a function definition can make it unsuitable for inline substitution.
Among these usages are: use of varargs, use of alloca, use of variable-sized data,
use of computed goto and use of nonlocal goto. Using the command-line option
-Winline
Among these usages are: use of varargs, use of alloca, use of variable-sized data,
use of computed goto and use of nonlocal goto. Using the command-line option
-Winline
will warn when a function marked inline could not be substituted, and will
give the reason for the failure.
In compiler syntax, the inline keyword does not affect the linkage of the function.
When a function is both inline and static, if all calls to the function are integrated
into the caller and the function’s address is never used, then the function’s own
assembler code is never referenced. In this case, the compiler does not actually output
assembler code for the function, unless you specify the command-line option
-fkeep-inline-functions
into the caller and the function’s address is never used, then the function’s own
assembler code is never referenced. In this case, the compiler does not actually output
assembler code for the function, unless you specify the command-line option
-fkeep-inline-functions
. Some calls cannot be integrated for various reasons
(in particular, calls that precede the function’s definition cannot be integrated and
neither can recursive calls within the definition). If there is a nonintegrated call, then the
function is compiled to assembler code as usual. The function must also be compiled
as usual if the program refers to its address, because that can’t be inlined. The compiler
will only eliminate inline functions if they are declared to be static and if the func-
tion definition precedes all uses of the function.
neither can recursive calls within the definition). If there is a nonintegrated call, then the
function is compiled to assembler code as usual. The function must also be compiled
as usual if the program refers to its address, because that can’t be inlined. The compiler
will only eliminate inline functions if they are declared to be static and if the func-
tion definition precedes all uses of the function.
When an inline function is not static, then the compiler must assume that there
may be calls from other source files. Since a global symbol can be defined only once
in any program, the function must not be defined in the other source files, so the calls
therein cannot be integrated. Therefore, a non-static inline function is always
compiled on its own in the usual fashion.
may be calls from other source files. Since a global symbol can be defined only once
in any program, the function must not be defined in the other source files, so the calls
therein cannot be integrated. Therefore, a non-static inline function is always
compiled on its own in the usual fashion.
If you specify both inline and extern in the function definition, then the definition is
used only for inlining. In no case is the function compiled on its own, not even if you
refer to its address explicitly. Such an address becomes an external reference, as if you
had only declared the function and had not defined it.
used only for inlining. In no case is the function compiled on its own, not even if you
refer to its address explicitly. Such an address becomes an external reference, as if you
had only declared the function and had not defined it.
This combination of inline and extern has a similar effect to a macro. Put a function
definition in a header file with these keywords and put another copy of the definition
(lacking inline and extern) in a library file. The definition in the header file will cause
most calls to the function to be inlined. If any uses of the function remain, they will refer
to the single copy in the library.
definition in a header file with these keywords and put another copy of the definition
(lacking inline and extern) in a library file. The definition in the header file will cause
most calls to the function to be inlined. If any uses of the function remain, they will refer
to the single copy in the library.