Patch-Source: https://github.com/archlinux/svntogit-packages/blob/bf2401407df5bcc938382eb03748fbef41e41c89/trunk/unbundle-jsoncpp-avoid-CFI-faults-with-is_cfi-true.patch
From ed8d931e35f81d8566835a579caf7d61368f85b7 Mon Sep 17 00:00:00 2001
From: Evangelos Foutras <evangelos@foutrelis.com>
Date: Tue, 27 Sep 2022 22:20:41 +0000
Subject: [PATCH] unbundle/jsoncpp: avoid CFI faults with is_cfi=true

Ensure jsoncpp symbols have public visibility and are thus excluded from
CFI checks and whole-program optimization. This is achieved by defining
JSON_DLL_BUILD which in turn causes json/config.h to define JSON_API as
__attribute__((visibility("default"))). The latter macro is used to tag
jsoncpp classes and namespace functions throughout jsoncpp's headers.

BUG=1365218

Change-Id: I56277737b7d9ecaeb5e17c8d21a2e55f3d5d5bc9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3919652
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1052077}
---
 build/linux/unbundle/jsoncpp.gn | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/build/linux/unbundle/jsoncpp.gn b/build/linux/unbundle/jsoncpp.gn
index 544f9d13c9..e84a0ef27a 100644
--- a/build/linux/unbundle/jsoncpp.gn
+++ b/build/linux/unbundle/jsoncpp.gn
@@ -3,6 +3,11 @@ import("//build/shim_headers.gni")
 
 pkg_config("jsoncpp_config") {
   packages = [ "jsoncpp" ]
+
+  # Defining JSON_DLL_BUILD applies public visibility to jsoncpp classes
+  # thus deactivating CFI checks for them. This avoids CFI violations in
+  # virtual calls to system jsoncpp library (https://crbug.com/1365218).
+  defines = [ "JSON_DLL_BUILD" ]
 }
 
 shim_headers("jsoncpp_shim") {
