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7.96 .section name

Use the .section directive to assemble the following code into a section named name.

This directive is only supported for targets that actually support arbitrarily named sections; on a.out targets, for example, it is not accepted, even with a standard a.out section name.

COFF Version

For COFF targets, the .section directive is used in one of the following ways:

     .section name[, "flags"]
     .section name[, subsection]

If the optional argument is quoted, it is taken as flags to use for the section. Each flag is a single character. The following flags are recognized:

b
bss section (uninitialized data)
n
section is not loaded
w
writable section
d
data section
r
read-only section
x
executable section
s
shared section (meaningful for PE targets)
a
ignored. (For compatibility with the ELF version)
y
section is not readable (meaningful for PE targets)
0-9
single-digit power-of-two section alignment (GNU extension)

If no flags are specified, the default flags depend upon the section name. If the section name is not recognized, the default will be for the section to be loaded and writable. Note the n and w flags remove attributes from the section, rather than adding them, so if they are used on their own it will be as if no flags had been specified at all.

If the optional argument to the .section directive is not quoted, it is taken as a subsection number (see Sub-Sections).

ELF Version

This is one of the ELF section stack manipulation directives. The others are .subsection (see SubSection), .pushsection (see PushSection), .popsection (see PopSection), and .previous (see Previous).

For ELF targets, the .section directive is used like this:

     .section name [, "flags"[, @type[,flag_specific_arguments]]]

The optional flags argument is a quoted string which may contain any combination of the following characters:

a
section is allocatable
w
section is writable
x
section is executable
M
section is mergeable
S
section contains zero terminated strings
G
section is a member of a section group
T
section is used for thread-local-storage

The optional type argument may contain one of the following constants:

@progbits
section contains data
@nobits
section does not contain data (i.e., section only occupies space)
@note
section contains data which is used by things other than the program
@init_array
section contains an array of pointers to init functions
@fini_array
section contains an array of pointers to finish functions
@preinit_array
section contains an array of pointers to pre-init functions

Many targets only support the first three section types.

Note on targets where the @ character is the start of a comment (eg ARM) then another character is used instead. For example the ARM port uses the % character.

If flags contains the M symbol then the type argument must be specified as well as an extra argument—entsize—like this:

     .section name , "flags"M, @type, entsize

Sections with the M flag but not S flag must contain fixed size constants, each entsize octets long. Sections with both M and S must contain zero terminated strings where each character is entsize bytes long. The linker may remove duplicates within sections with the same name, same entity size and same flags. entsize must be an absolute expression. For sections with both M and S, a string which is a suffix of a larger string is considered a duplicate. Thus "def" will be merged with "abcdef"; A reference to the first "def" will be changed to a reference to "abcdef"+3.

If flags contains the G symbol then the type argument must be present along with an additional field like this:

     .section name , "flags"G, @type, GroupName[, linkage]

The GroupName field specifies the name of the section group to which this particular section belongs. The optional linkage field can contain:

comdat
indicates that only one copy of this section should be retained
.gnu.linkonce
an alias for comdat

Note: if both the M and G flags are present then the fields for the Merge flag should come first, like this:

     .section name , "flags"MG, @type, entsize, GroupName[, linkage]

If no flags are specified, the default flags depend upon the section name. If the section name is not recognized, the default will be for the section to have none of the above flags: it will not be allocated in memory, nor writable, nor executable. The section will contain data.

For ELF targets, the assembler supports another type of .section directive for compatibility with the Solaris assembler:

     .section "name"[, flags...]

Note that the section name is quoted. There may be a sequence of comma separated flags:

#alloc
section is allocatable
#write
section is writable
#execinstr
section is executable
#tls
section is used for thread local storage

This directive replaces the current section and subsection. See the contents of the gas testsuite directory gas/testsuite/gas/elf for some examples of how this directive and the other section stack directives work.