build: Add a symbol version to all exported symbols for glibc
The --default-symver linker option attaches a default version definition (the SONAME) to every exported symbol. It is supported since at least GNU binutils 2.22 in 2011 (older versions not tested). With this version definition, newly-linked binaries that depend on the jansson 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-c or json-glib if those libraries appear in dependency search order before jansson, 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 parse_json() calls json_decref(). It does not affect calls from external code into jansson, unless jansson was statically linked into the external caller. This change will also not prevent code that depends on json-c or json-glib from finding jansson's symbols and crashing; to prevent that, a corresponding change in json-c or json-glib would be needed. Adding a symbol-version is a backwards-compatible change, but once added, removing or changing the symbol-version would be an incompatible change that requires a SONAME bump. Resolves: https://github.com/akheron/jansson/issues/523 (when combined with an equivalent change to json-c). Signed-off-by: Simon McVittie <smcv@collabora.com>
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@ -107,6 +107,9 @@ if (HAS_NO_FORMAT_TRUNCATION)
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set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-format-truncation")
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endif()
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include (CheckSymbolExists)
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check_symbol_exists("__GLIBC__" "stdlib.h" LIBC_IS_GLIBC)
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if (MSVC)
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# Turn off Microsofts "security" warnings.
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add_definitions( "/W3 /D_CRT_SECURE_NO_WARNINGS /wd4005 /wd4996 /nologo" )
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@ -366,6 +369,10 @@ if(JANSSON_BUILD_SHARED_LIBS)
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${JANSSON_HDR_PUBLIC}
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src/jansson.def)
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if (LIBC_IS_GLIBC)
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set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--default-symver")
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endif()
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set_target_properties(jansson PROPERTIES
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VERSION ${JANSSON_VERSION}
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SOVERSION ${JANSSON_SOVERSION})
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@ -137,6 +137,10 @@ fi
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AS_IF([test "x$with_Bsymbolic" = "xyes"], [JSON_BSYMBOLIC_LDFLAGS=-Wl[,]-Bsymbolic-functions])
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AC_SUBST(JSON_BSYMBOLIC_LDFLAGS)
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# Enable symbol versioning on GNU libc
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JSON_SYMVER_LDFLAGS=
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AC_CHECK_DECL([__GLIBC__], [JSON_SYMVER_LDFLAGS=-Wl,--default-symver])
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AC_SUBST([JSON_SYMVER_LDFLAGS])
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AC_ARG_ENABLE([ossfuzzers],
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[AS_HELP_STRING([--enable-ossfuzzers],
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@ -26,4 +26,5 @@ libjansson_la_LDFLAGS = \
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-no-undefined \
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-export-symbols-regex '^json_|^jansson_' \
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-version-info 17:0:13 \
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@JSON_SYMVER_LDFLAGS@ \
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@JSON_BSYMBOLIC_LDFLAGS@
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