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24.\" $Id: elf_getscn.3,v 1.2 2025/06/10 17:19:45 schwarze Exp $
25.\"
26.Dd September 24, 2018
27.Dt ELF_GETSCN 3
28.Os
29.Sh NAME
30.Nm elf_getscn ,
31.Nm elf_ndxscn ,
32.Nm elf_newscn ,
33.Nm elf_nextscn
34.Nd get/allocate section information for an ELF object
35.Sh SYNOPSIS
36.Lb libelf
37.In libelf.h
38.Ft "Elf_Scn *"
39.Fn elf_getscn "Elf *elf" "size_t index"
40.Ft size_t
41.Fn elf_ndxscn "Elf_Scn *scn"
42.Ft "Elf_Scn *"
43.Fn elf_newscn "Elf *elf"
44.Ft "Elf_Scn *"
45.Fn elf_nextscn "Elf *elf" "Elf_Scn *scn"
46.Sh DESCRIPTION
47These functions are used to iterate through the sections associated
48with an ELF descriptor.
49.Pp
50Function
51.Fn elf_getscn
52will return a section descriptor for the section at index
53.Ar index
54in the object denoted by ELF descriptor
55.Ar elf .
56An error will be signalled if the specified section does not
57exist.
58.Pp
59Function
60.Fn elf_ndxscn
61returns the section table index associated with section descriptor
62.Ar scn .
63.Pp
64Function
65.Fn elf_newscn
66creates a new section and appends it to the list of sections
67associated with descriptor
68.Ar elf .
69The library will automatically increment the
70.Va e_shnum
71field of the ELF header associated with descriptor
72.Ar elf ,
73and will set the
74.Dv ELF_F_DIRTY
75flag on the returned section descriptor.
76For ELF descriptors opened for writing, the ELF library will
77automatically create an empty section at index zero
78.Dv ( SHN_UNDEF )
79on the first call to
80.Fn elf_newscn .
81.Pp
82Function
83.Fn elf_nextscn
84takes a section descriptor
85.Ar scn
86and returns a pointer to the section descriptor at the next higher
87index.
88As a consequence,
89.Fn elf_nextscn
90will never return a pointer to the empty section at index zero
91.Dv ( SHN_UNDEF ) .
92Argument
93.Ar scn
94is allowed to be NULL, in which case this function will return a
95pointer to the section descriptor at index 1.
96If no further sections are present, function
97.Fn elf_nextscn
98will return a NULL pointer.
99.Sh RETURN VALUES
100Functions
101.Fn elf_getscn ,
102.Fn elf_newscn
103and
104.Fn elf_nextscn
105return a valid pointer to a section descriptor if successful, or
106NULL if an error occurs.
107.Pp
108Function
109.Fn elf_ndxscn
110returns a valid section table index if successful, or
111.Dv SHN_UNDEF
112if an error occurs.
113.Sh ERRORS
114These functions may fail with the following errors:
115.Bl -tag -width "[ELF_E_RESOURCE]"
116.It Bq Er ELF_E_ARGUMENT
117Arguments
118.Ar elf
119or
120.Ar scn
121were NULL.
122.It Bq Er ELF_E_ARGUMENT
123Argument
124.Ar index
125exceeded the current number of sections in the ELF object.
126.It Bq Er ELF_E_ARGUMENT
127Argument
128.Ar elf
129was not a descriptor for an ELF file.
130.It Bq Er ELF_E_ARGUMENT
131Section descriptor
132.Ar scn
133was not associated with ELF descriptor
134.Ar elf .
135.It Bq Er ELF_E_CLASS
136Descriptor
137.Ar elf
138was of an unknown ELF class.
139.It Bq Er ELF_E_SECTION
140Argument
141.Ar elf
142specified extended section numbering in the ELF header with the section header at
143index
144.Dv SHN_UNDEF
145not being of type
146.Dv SHT_NULL .
147.El
148.Sh SEE ALSO
149.Xr elf 3 ,
150.Xr elf_flagdata 3 ,
151.Xr elf_flagscn 3 ,
152.Xr elf_getdata 3 ,
153.Xr elf_getshdr 3 ,
154.Xr gelf 3