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[meta-oe,wrynose] capnproto: build position independent code

Message ID 20260902165307.1259305-1-joel.winarske@gmail.com
State New
Headers show
Series [meta-oe,wrynose] capnproto: build position independent code | expand

Commit Message

Joel Winarske Sept. 2, 2026, 4:53 p.m. UTC
The recipe produces static archives only, and does not compile them PIC, so
linking capnp or kj into a shared library fails:

  libkj.a(exception.c++.o): relocation R_X86_64_TPOFF32 against
  `kj::(anonymous namespace)::threadLocalCallback' can not be used when making
  a shared object; local-exec is incompatible with -shared

kj/exception.c++ has a file-scope thread_local, which non-PIC code compiles to
the local-exec TLS model. A shared object cannot use that model, so the link
fails on any consumer that puts capnp inside a .so. Debian and Fedora do not
hit this because they ship shared libcapnp.

Set CMAKE_POSITION_INDEPENDENT_CODE. Packaging is unchanged: still static,
still no .so, no new packages and no ABI surface, only the code model differs.

Backport of the same change sent for master, where the recipe is 1.5.0.

Signed-off-by: Joel Winarske <joel.winarske@gmail.com>
---
 meta-oe/recipes-devtools/capnproto/capnproto_1.4.0.bb | 9 +++++++++
 1 file changed, 9 insertions(+)
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Patch

diff --git a/meta-oe/recipes-devtools/capnproto/capnproto_1.4.0.bb b/meta-oe/recipes-devtools/capnproto/capnproto_1.4.0.bb
index 948ff80345..8c914d96bd 100644
--- a/meta-oe/recipes-devtools/capnproto/capnproto_1.4.0.bb
+++ b/meta-oe/recipes-devtools/capnproto/capnproto_1.4.0.bb
@@ -19,8 +19,17 @@  CXXFLAGS:append:mips = " -latomic"
 CXXFLAGS:append:powerpc = " -latomic"
 CXXFLAGS:append:riscv32 = " -latomic"
 
+# The build produces static archives only. Compile them position independent so
+# they can be linked into shared libraries; without this any consumer that does
+# so fails on the thread-local in kj/exception.c++, which non-PIC code compiles
+# to the local-exec TLS model:
+#
+#   libkj.a(exception.c++.o): relocation R_X86_64_TPOFF32 against
+#   `kj::(anonymous namespace)::threadLocalCallback' can not be used when making
+#   a shared object; local-exec is incompatible with -shared
 EXTRA_OECMAKE += "\
     -DBUILD_TESTING=OFF \
+    -DCMAKE_POSITION_INDEPENDENT_CODE=ON \
 "
 
 FILES:${PN}-compiler = "${bindir}"