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Khem Raj
53c0b99a78
posix_ipc decides at build time whether it needs librt and whether
message queues are available by compiling small probe programs in
build_support/discover_system_info.py. Its does_build_succeed() splices
the linker option into the compiler argv verbatim, so when no extra
library is wanted the compiler is called with a literal empty argument:
$CC -Wall -o foo foo.c '' -lpthread
GNU ld treats '' as an input file and fails ("cannot find : No such
file or directory"); lld ignores it. With the gcc toolchain every probe
without -lrt therefore fails, the prober wrongly decides librt is
required, and on a C library without a usable librt message queue
support is dropped - which is how posix_ipc.MessageQueue went missing
(issue #916). The result depends on the linker rather than on what the
C library provides.
The previous LDFLAGS += "-lrt" workaround only papered over this, and
is itself libc specific: it forces linking librt even where mq_* live
in libc (glibc >= 2.34, musl).
Fix the prober to split linker_options with shlex, like it already does
for CC, so an empty value adds no argument, and drop the forced -lrt so
the probes decide per C library.
Verified on qemux86-64 for glibc and musl, each with the clang and gcc
toolchains: src/system_info.h defines MESSAGE_QUEUE_SUPPORT_EXISTS,
SEM_GETVALUE_EXISTS and SEM_TIMEDWAIT_EXISTS, and the extension module
imports all mq_* from libc with no librt NEEDED entry.
Fixes: https://github.com/openembedded/meta-openembedded/issues/916
AI-Generated: Uses Claude Code
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
47 lines
2.0 KiB
Diff
47 lines
2.0 KiB
Diff
From a2d268590cd2e8460b40438b4eff894ae472a0f2 Mon Sep 17 00:00:00 2001
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From: Khem Raj <khem.raj@oss.qualcomm.com>
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Date: Fri, 16 Oct 2026 16:26:28 +0000
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Subject: [PATCH] build_support: do not pass empty linker option to the
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compiler
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does_build_succeed() builds an argv list and inserts linker_options
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verbatim. When no extra linker option is wanted it is "", so the
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compiler is invoked with a literal empty argument:
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cc -Wall -o foo foo.c '' -lpthread
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GNU ld treats the empty argument as an input file and fails with
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"cannot find : No such file or directory", while lld silently ignores
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it. With GNU ld every probe that runs without -lrt therefore fails,
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which makes sniff_realtime_lib() wrongly conclude that librt is needed
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(or raise DiscoveryError on C libraries that have no usable librt),
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independent of what the C library actually provides. With lld the
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probes happen to give the right answer, so the outcome depends on the
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linker rather than on the target system.
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This regressed when the command was converted from a shell string
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(where an empty %s vanished) to an argv list.
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Split linker_options with shlex like CC already is, so an empty value
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contributes no argument and multi-word values still work.
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Upstream-Status: Submitted [https://github.com/osvenskan/posix_ipc/pull/114]
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Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
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---
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build_support/discover_system_info.py | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/build_support/discover_system_info.py b/build_support/discover_system_info.py
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index 1c3741f..669c234 100644
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--- a/build_support/discover_system_info.py
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+++ b/build_support/discover_system_info.py
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@@ -57,7 +57,7 @@ def does_build_succeed(filename, linker_options=""):
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'-o',
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f'./build_support/src/{filename[:-2]}',
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f'./build_support/src/{filename}',
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- linker_options,
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+ *shlex.split(linker_options),
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'-lpthread'
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]
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p = subprocess.Popen(cmd, stdout=STDOUT, stderr=STDERR)
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