From: Nick Clifton <nickc@sourceware.org>
To: bfd-cvs@sourceware.org
Subject: [binutils-gdb] Fix: symbols eliminated by --gc-sections still trigger warnings for gnu.warning.SYM
Date: Tue, 21 Nov 2023 09:27:09 +0000 (GMT) [thread overview]
Message-ID: <20231121092709.4F36D3858D33@sourceware.org> (raw)
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=1c320501655ec8d5077d0a3231652c7d661249bc
commit 1c320501655ec8d5077d0a3231652c7d661249bc
Author: Nick Clifton <nickc@redhat.com>
Date: Tue Nov 21 09:26:19 2023 +0000
Fix: symbols eliminated by --gc-sections still trigger warnings for gnu.warning.SYM
PR 31067
* linker.c (_bfd_generic_link_add_one_symbol): When issuing a warning message, also display a message about the warning not being affected by garbage colleciton.
* ld.texi (Special Sections): New entry in the linker manual. Describes how the .gnu.warning and .gnu.warning.SYM sections behave.
Diff:
---
bfd/ChangeLog | 7 +++++++
bfd/linker.c | 8 ++++++++
ld/ChangeLog | 7 +++++++
ld/ld.texi | 45 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 67 insertions(+)
diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 143069894c1..e9f571acac2 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,10 @@
+2023-11-21 Nick Clifton <nickc@redhat.com>
+
+ PR 31067
+ linker.c (_bfd_generic_link_add_one_symbol): When issuing a
+ warning message, also display a message about the warning not
+ being affected by garbage colleciton.
+
2023-11-15 Arsen Arsenović <arsen@aarsen.me>
* aclocal.m4: Regenerate.
diff --git a/bfd/linker.c b/bfd/linker.c
index 28fffc3ad63..90dc581cfe3 100644
--- a/bfd/linker.c
+++ b/bfd/linker.c
@@ -1784,6 +1784,14 @@ _bfd_generic_link_add_one_symbol (struct bfd_link_info *info,
{
(*info->callbacks->warning) (info, string, h->root.string,
hash_entry_bfd (h), NULL, 0);
+ /* PR 31067: If garbage collection is enabled then the
+ referenced symbol may actually be discarded later on.
+ This could be very confusing to the user. So give them
+ a hint as to what might be happening. */
+ if (info->gc_sections)
+ (*info->callbacks->info)
+ (_("%P: %pB: note: the message above does not take linker garbage collection into account\n"),
+ hash_entry_bfd (h));
break;
}
/* Fall through. */
diff --git a/ld/ChangeLog b/ld/ChangeLog
index a30d3ad39b6..1766bd86dc2 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,10 @@
+2023-11-21 Nick Clifton <nickc@redhat.com>
+
+ PR 31067
+ * ld.texi (Special Sections): New entry in the linker manual.
+ Describes how the .gnu.warning and .gnu.warning.SYM sections
+ behave.
+
2023-11-15 Arsen Arsenović <arsen@aarsen.me>
* aclocal.m4: Regenerate.
diff --git a/ld/ld.texi b/ld/ld.texi
index 5a143b2b518..0704eece8d6 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -127,6 +127,7 @@ in the section entitled ``GNU Free Documentation License''.
* Invocation:: Invocation
* Scripts:: Linker Scripts
* Plugins:: Linker Plugins
+* Special Sections:: Special Sections
@ifset GENERIC
* Machine Dependent:: Machine Dependent Features
@end ifset
@@ -7525,6 +7526,50 @@ the @samp{__.LIBDEP} member of @file{libssl.a} would contain
-L/usr/local/lib -lcrypto
@end smallexample
+@node Special Sections
+When linking ELF format object files @command{ld} treats some sections
+in a special, non standard manner. This part of the manual describes
+these sections.
+
+@table @gcctabopt
+@item .gnu.warning
+The contents of any section with this name are assumed to be an ascii
+format warning message. The contents will be displayed to the user if
+the sections appears in any input file, but the section will not be
+copied into the output image. If the @option{--fatal-warnings} option
+is enabled then the warnings - if any are encountered - will also stop
+the link from completing.
+
+Note - the @samp{.gnu.warning} section is not subject to linker
+garbage collection or orphan handling.
+
+@item .gnu.warning.@var{SYM}
+The contents of any section whoes name starts with the prefix
+@samp{.gnu.warning.} and then finishes with the name of a symbol is
+treated in a similar fashion to the @samp{.gnu.warning} section, but
+only if the named symbol is defined. So for example the contents of a
+section called @samp{.gnu.warning.foo} will be displayed as warning
+message if, and only if, the symbol @samp{foo} is defined by one or
+more of the input files. This includes object files pulled in from
+static libraries, shared objects needed to complete the link and so
+on.
+
+Note - because these warning messages are generated before the linker
+performs garbage collection (if enabled) it is possible for a warning
+to be displayed for a symbol that is later removed and then never
+appears in the final output.
+
+@item .note.gnu.property
+When the linker combines sections of this name it will merge them
+together according to various rules encoded into the notes
+themselves. Therefore the contents of the output .note.gnu.property
+section may not correspond to a simple concatenation of the input
+sections. If the @option{-Map} option has been used to request a
+linker map then details of any property merging will be included in
+the map.
+
+@end table
+
@ifset GENERIC
@node Machine Dependent
@chapter Machine Dependent Features
next reply other threads:[~2023-11-21 9:27 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-21 9:27 Nick Clifton [this message]
2023-11-21 11:31 Nick Clifton
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