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Preface armclang Command-line Options Compiler-specific Keywords and Operators Compiler-specific Function, Variable, and Type Att Function attributes __attribute__((always_inline)) function attribute __attribute__((cmse_nonsecure_call)) function attr __attribute__((cmse_nonsecure_entry)) function att __attribute__((const)) function attribute __attribute__((constructor(priority))) function at __attribute__((format_arg(string-index))) function __attribute__((interrupt("type"))) function attrib __attribute__((malloc)) function attribute __attribute__((naked)) function attribute __attribute__((noinline)) function attribute __attribute__((nonnull)) function attribute __attribute__((noreturn)) function attribute __attribute__((nothrow)) function attribute __attribute__((pcs("calling_convention"))) functio __attribute__((pure)) function attribute __attribute__((section("name"))) function attribut __attribute__((unused)) function attribute __attribute__((used)) function attribute __attribute__((value_in_regs)) function attribute __attribute__((visibility("visibility_type"))) fun __attribute__((weak)) function attribute __attribute__((weakref("target"))) function attrib Type attributes __attribute__((aligned)) type attribute __attribute__((packed)) type attribute __attribute__((transparent_union)) type attribute Variable attributes __attribute__((alias)) variable attribute __attribute__((aligned)) variable attribute __attribute__((deprecated)) variable attribute __attribute__((packed)) variable attribute __attribute__((section("name"))) variable attribut __attribute__((unused)) variable attribute __attribute__((used)) variable attribute __attribute__((visibility("visibility_type"))) var __attribute__((weak)) variable attribute __attribute__((weakref("target"))) variable attrib Compiler-specific Intrinsics Compiler-specific Pragmas Other Compiler-specific Features Standard C Implementation Definition Standard C++ Implementation Definition armclang Integrated Assembler armclang Inline Assembler

__attribute__((unused)) function attribute

3.18 __attribute__((unused)) function attribute

The unused function attribute prevents the compiler from generating warnings if the function is not referenced. This does not change the behavior of the unused function removal process.

Note:

By default, the compiler does not warn about unused functions. Use -Wunused-function to enable this warning specifically, or use an encompassing -W value such as -Wall.

The __attribute__((unused)) attribute can be useful if you usually want to warn about unused functions, but want to suppress warnings for a specific set of functions.

Example

static int unused_no_warning(int b) __attribute__((unused));
static int unused_no_warning(int b)
{
  return b++;
}

static int unused_with_warning(int b);
static int unused_with_warning(int b)
{
  return b++;
}

Compiling this example with -Wall results in the following warning:

armclang --target=aarch64-arm-none-eabi -c test.c -Wall
test.c:10:12: warning: unused function 'unused_with_warning' [-Wunused-function]
static int unused_with_warning(int b)
           ^
1 warning generated.
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