Using and Porting GNU CC - Label Output

Output and Generation of Labels

This is about outputting labels.

ASM_OUTPUT_LABEL (stream, name)

A C statement (sans semicolon) to output to the stdio stream stream the assembler definition of a label named name. Use the expression assemble_name (stream, name) to output the name itself; before and after that, output the additional assembler syntax for defining the name, and a newline.

ASM_DECLARE_FUNCTION_NAME (stream, name, decl)

A C statement (sans semicolon) to output to the stdio stream stream any text necessary for declaring the name name of a function which is being defined. This macro is responsible for outputting the label definition (perhaps using ASM_OUTPUT_LABEL ). The argument decl is the FUNCTION_DECL tree node representing the function.

If this macro is not defined, then the function name is defined in the usual manner as a label (by means of ASM_OUTPUT_LABEL ).

ASM_DECLARE_FUNCTION_SIZE (stream, name, decl)

A C statement (sans semicolon) to output to the stdio stream stream any text necessary for declaring the size of a function which is being defined. The argument name is the name of the function. The argument decl is the FUNCTION_DECL tree node representing the function.

If this macro is not defined, then the function size is not defined.

ASM_DECLARE_OBJECT_NAME (stream, name, decl)

A C statement (sans semicolon) to output to the stdio stream stream any text necessary for declaring the name name of an initialized variable which is being defined. This macro must output the label definition (perhaps using ASM_OUTPUT_LABEL ). The argument decl is the VAR_DECL tree node representing the variable.

If this macro is not defined, then the variable name is defined in the usual manner as a label (by means of ASM_OUTPUT_LABEL ).

ASM_FINISH_DECLARE_OBJECT (stream, decl, toplevel, atend)

A C statement (sans semicolon) to finish up declaring a variable name once the compiler has processed its initializer fully and thus has had a chance to determine the size of an array when controlled by an initializer. This is used on systems where it's necessary to declare something about the size of the object.

If you don't define this macro, that is equivalent to defining it to do nothing.

ASM_GLOBALIZE_LABEL (stream, name)

A C statement (sans semicolon) to output to the stdio stream stream some commands that will make the label name global; that is, available for reference from other files. Use the expression assemble_name (stream, name) to output the name itself; before and after that, output the additional assembler syntax for making that name global, and a newline.

ASM_WEAKEN_LABEL

A C statement (sans semicolon) to output to the stdio stream stream some commands that will make the label name weak; that is, available for reference from other files but only used if no other definition is available. Use the expression assemble_name (stream, name) to output the name itself; before and after that, output the additional assembler syntax for making that name weak, and a newline.

If you don't define this macro, GNU CC will not support weak symbols and you should not define the SUPPORTS_WEAK macro.

SUPPORTS_WEAK

A C expression which evaluates to true if the target supports weak symbols.

If you don't define this macro, `defaults.h' provides a default definition. If ASM_WEAKEN_LABEL is defined, the default definition is `1'; otherwise, it is `0'. Define this macro if you want to control weak symbol support with a compiler flag such as `-melf'.

ASM_OUTPUT_EXTERNAL (stream, decl, name)

A C statement (sans semicolon) to output to the stdio stream stream any text necessary for declaring the name of an external symbol named name which is referenced in this compilation but not defined. The value of decl is the tree node for the declaration.

This macro need not be defined if it does not need to output anything. The GNU assembler and most Unix assemblers don't require anything.

ASM_OUTPUT_EXTERNAL_LIBCALL (stream, symref)

A C statement (sans semicolon) to output on stream an assembler pseudo-op to declare a library function name external. The name of the library function is given by symref, which has type rtx and is a symbol_ref .

This macro need not be defined if it does not need to output anything. The GNU assembler and most Unix assemblers don't require anything.

ASM_OUTPUT_LABELREF (stream, name)

A C statement (sans semicolon) to output to the stdio stream stream a reference in assembler syntax to a label named name. This should add `_' to the front of the name, if that is customary on your operating system, as it is in most Berkeley Unix systems. This macro is used in assemble_name .

ASM_OUTPUT_INTERNAL_LABEL (stream, prefix, num)

A C statement to output to the stdio stream stream a label whose name is made from the string prefix and the number num.

It is absolutely essential that these labels be distinct from the labels used for user-level functions and variables. Otherwise, certain programs will have name conflicts with internal labels.

It is desirable to exclude internal labels from the symbol table of the object file. Most assemblers have a naming convention for labels that should be excluded; on many systems, the letter `L' at the beginning of a label has this effect. You should find out what convention your system uses, and follow it.

The usual definition of this macro is as follows:

	fprintf (stream, "L%s%d:\n", prefix, num)

ASM_GENERATE_INTERNAL_LABEL (string, prefix, num)

A C statement to store into the string string a label whose name is made from the string prefix and the number num.

This string, when output subsequently by assemble_name , should produce the output that ASM_OUTPUT_INTERNAL_LABEL would produce with the same prefix and num.

If the string begins with `*', then assemble_name will output the rest of the string unchanged. It is often convenient for ASM_GENERATE_INTERNAL_LABEL to use `*' in this way. If the string doesn't start with `*', then ASM_OUTPUT_LABELREF gets to output the string, and may change it. (Of course, ASM_OUTPUT_LABELREF is also part of your machine description, so you should know what it does on your machine.)

ASM_FORMAT_PRIVATE_NAME (outvar, name, number)

A C expression to assign to outvar (which is a variable of type char * ) a newly allocated string made from the string name and the number number, with some suitable punctuation added. Use alloca to get space for the string.

The string will be used as an argument to ASM_OUTPUT_LABELREF to produce an assembler label for an internal static variable whose name is name. Therefore, the string must be such as to result in valid assembler code. The argument number is different each time this macro is executed; it prevents conflicts between similarly-named internal static variables in different scopes.

Ideally this string should not be a valid C identifier, to prevent any conflict with the user's own symbols. Most assemblers allow periods or percent signs in assembler symbols; putting at least one of these between the name and the number will suffice.

ASM_OUTPUT_DEF (stream, name, value)

A C statement to output to the stdio stream stream assembler code which defines (equates) the symbol name to have the value value.

If SET_ASM_OP is defined, a default definition is provided which is correct for most systems.

OBJC_GEN_METHOD_LABEL (buf, is_inst, class_name, cat_name, sel_name)

Define this macro to override the default assembler names used for Objective C methods.

The default name is a unique method number followed by the name of the class (e.g. `_1_Foo'). For methods in categories, the name of the category is also included in the assembler name (e.g. `_1_Foo_Bar').

These names are safe on most systems, but make debugging difficult since the method's selector is not present in the name. Therefore, particular systems define other ways of computing names.

buf is an expression of type char * which gives you a buffer in which to store the name; its length is as long as class_name, cat_name and sel_name put together, plus 50 characters extra.

The argument is_inst specifies whether the method is an instance method or a class method; class_name is the name of the class; cat_name is the name of the category (or NULL if the method is not in a category); and sel_name is the name of the selector.

On systems where the assembler can handle quoted names, you can use this macro to provide more human-readable names.