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build: Add symbol versions to all exported symbols

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With this version script, newly-linked binaries that depend on the
json-c shared library will refer to its symbols in a versioned form,
preventing their references from being resolved to a symbol of the same
name exported by json-glib or libjansson if those libraries appear in
dependency search order before json-c, which will usually result in
a crash. This is necessary because ELF symbol resolution normally uses
a single flat namespace, not a tree like Windows symbol resolution.
At least one symbol (json_object_iter_next()) is exported by all three
JSON libraries.

Linking with -Bsymbolic is not enough to have this effect in all cases,
because -Bsymbolic only affects symbol lookup within a shared object,
for example when json_object_set_serializer() calls
json_object_set_userdata(). It does not affect calls from external
code into json-c, unless json-c was statically linked into the
external caller.

This change will also not prevent code that depends on json-glib or
libjansson from finding json-c's symbols and crashing; to prevent
that, a corresponding change in json-glib or libjansson would be needed.

Adding a symbol-version is a backwards-compatible change, but once
added, removing or changing the symbol-version on a symbol would be an
incompatible change that requires a SONAME bump.

Resolves: https://github.com/json-c/json-c/issues/621
(when combined with an equivalent change to libjansson).

Signed-off-by: Simon McVittie <smcv@collabora.com>
This commit is contained in:
Simon McVittie
2020-06-29 18:16:34 +01:00
parent 34334e5d3f
commit c2c94024f5
2 changed files with 169 additions and 0 deletions
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16
CMakeLists.txt
View File

@@ -325,6 +325,22 @@ if (NOT ("${CMAKE_C_COMPILER_ID}" STREQUAL "MSVC"))
# XXX need cmake>=3.13 for this:
#add_link_options("-Wl,-Bsymbolic-functions")
endif()
file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/check-version-script.sym" "TEST { global: *; };")
list(APPEND CMAKE_REQUIRED_LIBRARIES "-Wl,--version-script,${CMAKE_CURRENT_BINARY_DIR}/check-version-script.sym")
check_c_source_compiles(
"
int main (void)
{
return 0;
}
"
VERSION_SCRIPT_WORKS
)
list(REMOVE_ITEM CMAKE_REQUIRED_LIBRARIES "-Wl,--version-script,${CMAKE_CURRENT_BINARY_DIR}/check-version-script.sym")
if (VERSION_SCRIPT_WORKS)
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--version-script,${CMAKE_CURRENT_SOURCE_DIR}/json-c.sym")
endif()
endif()
if ($ENV{VALGRIND})