'\" t
.TH "SD_ELF_NOTE_DLOPEN" "3" "" "systemd 261.1" "SD_ELF_NOTE_DLOPEN"
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.SH "NAME"
SD_ELF_NOTE_DLOPEN, SD_ELF_NOTE_DLOPEN_VENDOR, SD_ELF_NOTE_DLOPEN_TYPE, SD_ELF_NOTE_DLOPEN_PRIORITY_REQUIRED, SD_ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED, SD_ELF_NOTE_DLOPEN_PRIORITY_SUGGESTED \- Embed ELF \&.note\&.dlopen metadata for shared library dependencies
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-dlopen\&.h>
.fi
.ft
.sp
.ft B
.nf
SD_ELF_NOTE_DLOPEN(\fIfeature\fR, \fIdescription\fR, \fIpriority\fR, \fIsoname\&.\&.\&.\fR)
.fi
.ft
.sp
.ft B
.nf
#define SD_ELF_NOTE_DLOPEN_VENDOR "FDO"
.fi
.ft
.sp
.ft B
.nf
#define SD_ELF_NOTE_DLOPEN_TYPE UINT32_C(0x407c0c0a)
.fi
.ft
.sp
.ft B
.nf
#define SD_ELF_NOTE_DLOPEN_PRIORITY_REQUIRED    "required"
.fi
.ft
.sp
.ft B
.nf
#define SD_ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED "recommended"
.fi
.ft
.sp
.ft B
.nf
#define SD_ELF_NOTE_DLOPEN_PRIORITY_SUGGESTED   "suggested"
.fi
.ft
.SH "DESCRIPTION"
.PP
\fBSD_ELF_NOTE_DLOPEN()\fR
is a macro that embeds a
\&.note\&.dlopen
ELF note section in the compiled binary, declaring a weak dependency on a shared library loaded via
\fBdlopen()\fR\&. This implements the
\m[blue]\fBELF dlopen metadata\fR\m[]\&\s-2\u[1]\d\s+2
specification, allowing package managers and build systems to discover runtime dependencies that are not visible through regular ELF
\fBDT_NEEDED\fR
entries\&.
.PP
The macro takes the following parameters:
.PP
\fIfeature\fR
.RS 4
A short string identifying the feature this library provides (e\&.g\&.
"XKB",
"PCRE2")\&.
.sp
Added in version 261\&.
.RE
.PP
\fIdescription\fR
.RS 4
A human\-readable description of what the library is used for\&.
.sp
Added in version 261\&.
.RE
.PP
\fIpriority\fR
.RS 4
One of
\fBSD_ELF_NOTE_DLOPEN_PRIORITY_REQUIRED\fR,
\fBSD_ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED\fR, or
\fBSD_ELF_NOTE_DLOPEN_PRIORITY_SUGGESTED\fR, indicating how important the dependency is\&.
.sp
Added in version 261\&.
.RE
.PP
\fIsoname\&.\&.\&.\fR
.RS 4
One or more shared object names (sonames) for the library, e\&.g\&.
"libfoo\&.so\&.1"\&. Multiple sonames may be specified as separate arguments (up to 5) for libraries that have changed soname across versions\&.
.sp
Added in version 261\&.
.RE
.PP
The embedded metadata can be read from a compiled ELF binary using:
.sp
.if n \{\
.RS 4
.\}
.nf
systemd\-analyze dlopen\-metadata \fIbinary\fR
.fi
.if n \{\
.RE
.\}
.SH "EXAMPLES"
.PP
\fBExample\ \&1.\ \&Single soname\fR
.sp
.if n \{\
.RS 4
.\}
.nf
#include <systemd/sd\-dlopen\&.h>

SD_ELF_NOTE_DLOPEN("XKB", "Keyboard layout support",
                    SD_ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED,
                    "libxkbcommon\&.so\&.0");
.fi
.if n \{\
.RE
.\}
.PP
\fBExample\ \&2.\ \&Multiple sonames for different library versions\fR
.sp
.if n \{\
.RS 4
.\}
.nf
SD_ELF_NOTE_DLOPEN("crypt", "Support for hashing passwords",
                    SD_ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED,
                    "libcrypt\&.so\&.2", "libcrypt\&.so\&.1", "libcrypt\&.so\&.1\&.1");
.fi
.if n \{\
.RE
.\}
.SH "NOTES"
.PP
The macros described here are header\-only and do not require runtime linkage against
\fBlibsystemd\fR(3)\&. Only the installed header and include path (as provided by
\fBpkg\-config \-\-cflags libsystemd\fR) are needed\&.
.SH "HISTORY"
.PP
\fBSD_ELF_NOTE_DLOPEN()\fR,
\fBSD_ELF_NOTE_DLOPEN_VENDOR\fR,
\fBSD_ELF_NOTE_DLOPEN_TYPE\fR,
\fBSD_ELF_NOTE_DLOPEN_PRIORITY_REQUIRED\fR,
\fBSD_ELF_NOTE_DLOPEN_PRIORITY_RECOMMENDED\fR, and
\fBSD_ELF_NOTE_DLOPEN_PRIORITY_SUGGESTED\fR
were added in version 261\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBsd-dlopen\fR(3), \fBdlopen\fR(3)
.SH "NOTES"
.IP " 1." 4
ELF dlopen metadata
.RS 4
\%https://uapi-group.org/specifications/specs/elf_dlopen_metadata/
.RE