From 6a1481b9fde3e17f57cd23101ee4dc9319b5a6e5 Mon Sep 17 00:00:00 2001
From: Oliver Lantwin <oliver.lantwin@cern.ch>
Date: Fri, 5 Jun 2026 16:08:52 +0200
Subject: [PATCH] fix(geomodel): also hide std::__format vtables/typeinfo from
 exports
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PR #17 added `-Wl,--version-script={local: _ZNSt8__format*;}` which
hid `_ZN…`-mangled function symbols. Local audit confirmed 0 weak
`_ZN` exports per geomodel lib. But CI debug PR (ShipSoft/Geometry#29)
captured a backtrace showing the crash is still in libGeoModelWrite:

  Program received signal SIGSEGV
  #0 std::__format::_Sink<char>::_M_write(…) from libGeoModelWrite.so.6
  #1 std::__format::_Formatting_scanner<…>::_M_on_chars(…) from libGeoModelWrite.so.6
  #2 std::__format::_Scanner<char>::_M_scan(…) at <format>:3942
  …
  #7 SHiPGeometry::CalorimeterFactory::buildStack(…) at CalorimeterFactory.cpp:184

`nm -D libGeoModelWrite.so.6 | grep __format` still shows 15 entries
(all `V` vague-linkage) for vtables (`_ZTV…`), typeinfo (`_ZTI…`), and
typeinfo names (`_ZTS…`) of _Sink<char>, _Buf_sink, _Fixedbuf_sink,
_Seq_sink<string>, _Scanner, _Formatting_scanner. Those are not matched
by `_ZNSt8__format*` (they start with `_ZTV`/`_ZTI`/`_ZTS`, not `_ZN`),
so build_geometry's `_Seq_sink<string>` constructor still binds its
vptr to libGeoModelWrite's vtable, and the virtual call lands in
libGeoModelWrite's compiled-with-different-headers `_M_write`.

Broaden the version script pattern to `*NSt8__format*` so vtables,
typeinfo, typeinfo names, and any future nested std::__format symbols
all get localized. Bump build.number to 4.
---
 recipes/geomodel/build.sh    | 24 ++++++++++++++++--------
 recipes/geomodel/recipe.yaml |  2 +-
 2 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/recipes/geomodel/build.sh b/recipes/geomodel/build.sh
index 183e4da..8759c3a 100644
--- a/recipes/geomodel/build.sh
+++ b/recipes/geomodel/build.sh
@@ -1,15 +1,23 @@
 #!/bin/bash -e
 
-# Hide std::__format weak template instantiations from the dynamic symbol
-# table of every shared library produced here. libstdc++.so does not export
-# strong overrides for them, so without this script the weak duplicates baked
-# into libGeoModel{Xml,Write,Read,DBManager} become the only definitions the
-# dynamic linker can see, and subtle libstdcxx-devel header drift between the
-# geomodel build host and downstream consumers crashes std::format users at
-# runtime (ShipSoft/Geometry#26).
+# Hide every std::__format symbol from the dynamic symbol table of every
+# shared library produced here, including vtables, typeinfo, typeinfo names,
+# and template-instantiated functions. libstdc++.so does not export strong
+# overrides for them, so without this script the weak/vague-linkage copies
+# baked into libGeoModel{Xml,Write,Read,DBManager} become the only definitions
+# the dynamic linker can see; subtle libstdcxx-devel header drift between the
+# geomodel build host and downstream consumers then crashes std::format users
+# at runtime (ShipSoft/Geometry#26).
+#
+# The mangled namespace prefix `St8__format` matches every mangling form we
+# need to hide:
+#   _ZNSt8__format…  functions
+#   _ZTVNSt8__format…  vtables
+#   _ZTINSt8__format…  typeinfo
+#   _ZTSNSt8__format…  typeinfo names
 cat > "${SRC_DIR}/hide-std-format.ver" <<'EOF'
 {
-  local: _ZNSt8__format*;
+  local: *NSt8__format*;
 };
 EOF
 
diff --git a/recipes/geomodel/recipe.yaml b/recipes/geomodel/recipe.yaml
index 1db1079..bfa086e 100644
--- a/recipes/geomodel/recipe.yaml
+++ b/recipes/geomodel/recipe.yaml
@@ -10,7 +10,7 @@ source:
   sha256: 018c5087b70d956793d06dc040f842018eb3bedd9b2f175c6090af63ce963408
 
 build:
-  number: 3
+  number: 4
   skip:
     - win
   script: build.sh