Since being 'self-contained' is something I care about, I've been
bothered for years by an issue where, using a self-built Yocto image
with a built-in build appliance, I hit a failure in libcxx-native as
soon as TOOLCHAIN = "clang" is used. With the help of claude.ai and a
lot of debugging, I put together this patch, which fixes my problem.
On Wed, Aug 12 2026 at 18:13:40 +02:00:00, Markus Volk via
lists.openembedded.org <[email protected]> wrote:
do_preconfigure builds Distro::IsOpenEmbedded() from
CLANG_EXTRA_OE_DISTRO,
but two bugs silently defeat OE-host detection for any distro beyond
the shipped default (poky:poky).
The check is assembled by appending each entry as 'NAME ||' and
stripping the trailing operator, so only the first entry gets a
'DistroVal ==' prefix.
With more than one entry this generates e.g.:
bool IsOpenEmbedded() const { return DistroVal == POKY
||WAYLAND_DESKTOP; }
and compiles but IsOpenEmbedded() then always returns true regardless
of the
actual distro, since a non-zero enumerator is truthy -- the check
becomes
disabled rather than extended.
Separately, the .Case() match string is built from the
underscore-converted identifier (needed since it doubles as a C++
enumerator name) instead of the raw distro id as it appears in
/etc/os-release. Since detection compares directly against the raw
ID= value, any distro name containing a hyphen never matches.
This only surfaces on a self-hosted OE build host (e.g. via
packagegroup-core-buildessential/-core-sdk) with a non-'poky' DISTRO
registered in CLANG_EXTRA_OE_DISTRO. Mainstream distros never hit
this path, since their native GCC keeps crt objects and headers
together in one directory that clang's default search already finds.
OE-built hosts split these across two directories, which is exactly
what the IsOpenEmbedded()-gated candidate exists to handle -- with it
disabled, native clang-toolchain builds (e.g. libcxx-native) fail:
/usr/bin/x86_64-oe-linux-ld: cannot find crtbeginS.o: No such
file or directory
/usr/bin/x86_64-oe-linux-ld: cannot find -lgcc: No such file or
directory
Verified with debug instrumentation in
GCCInstallationDetector::ScanLibDirForGCCTriple(): with both fixes
applied, clang -v correctly reports:
Found candidate GCC installation: /usr/lib/x86_64-oe-linux/16.1.0
Selected GCC installation: /usr/lib/x86_64-oe-linux/16.1.0
Build each comparison explicitly and join with ' || ', and use the
raw (hyphenated) distro id for the .Case() match while keeping the
underscore-converted identifier only for the generated C++
enumerator/method names.
Signed-off-by: Markus Volk <[email protected]
<mailto:[email protected]>>
Co-authored-by: Claude <[email protected]
<mailto:[email protected]>>
---
meta/recipes-devtools/clang/llvm-project-source.inc | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/meta/recipes-devtools/clang/llvm-project-source.inc
b/meta/recipes-devtools/clang/llvm-project-source.inc
index 85b5ef06dc..5cd08d4085 100644
--- a/meta/recipes-devtools/clang/llvm-project-source.inc
+++ b/meta/recipes-devtools/clang/llvm-project-source.inc
@@ -65,18 +65,19 @@ python do_preconfigure() {
triple = ""
name = ""
check = ""
- oe_names = ""
+ oe_names = []
distros = d.getVar('CLANG_EXTRA_OE_DISTRO')
for distro in distros.split():
- distro_id = distro.split(":")[0].replace('-','_')
+ distro_id_raw = distro.split(":")[0]
+ distro_id = distro_id_raw.replace('-','_')
distro_triple = distro.split(":")[1]
- case += '\\n .Case("' + distro_id + '", Distro::' +
distro_id.upper() + ')'
+ case += '\\n .Case("' + distro_id_raw + '", Distro::' +
distro_id.upper() + ')'
triple += '\\n if (Distro.Is' + distro_id.upper() +
'())\\n return "x86_64-' + distro_triple + '-linux";'
name += '\\n '+ distro_id.upper() + ','
check += '\\nbool Is' + distro_id.upper() + '() const {
return DistroVal == ' + distro_id.upper() + '; }'
- oe_names += distro_id.upper() + ' ||'
+ oe_names.append('DistroVal == ' + distro_id.upper())
- check += '\\nbool IsOpenEmbedded() const { return DistroVal == '
+ oe_names[0:-3] + '; }'
+ check += '\\nbool IsOpenEmbedded() const { return ' + ' ||
'.join(oe_names) + '; }'
cmd = ['sed', '-i', 's#//CLANG_EXTRA_OE_DISTRO_NAME#%s#g' %
name, source + '/clang/include/clang/Driver/Distro.h']
subprocess.check_output(cmd, stderr=subprocess.STDOUT)
--
2.55.0
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