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From f15e8b573ada0fcd643ae393484214b1c7c940f8 Mon Sep 17 00:00:00 2001
From: Evangelos Foutras <evangelos@foutrelis.com>
Date: Sat, 24 Mar 2018 00:04:33 +0000
Subject: [PATCH] Fix crash in is_cfi=true builds with unbundled ICU
Ensure ICU symbols have public visibility and are thus excluded from CFI
checks and whole-program optimization. The former caused a startup crash
and the latter has the potential to break virtual calls in weird ways.
BUG=822820
Change-Id: Ia809eefcb9e93b3c612f2381d394db83bbc67120
Reviewed-on: https://chromium-review.googlesource.com/978008
Reviewed-by: Peter Collingbourne <pcc@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545638}
---
build/linux/unbundle/icu.gn | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/build/linux/unbundle/icu.gn b/build/linux/unbundle/icu.gn
index 5bdd91555df7..4450e409dba5 100644
--- a/build/linux/unbundle/icu.gn
+++ b/build/linux/unbundle/icu.gn
@@ -17,6 +17,24 @@ config("icu_config") {
"USING_SYSTEM_ICU=1",
"ICU_UTIL_DATA_IMPL=ICU_UTIL_DATA_STATIC",
"UCHAR_TYPE=uint16_t",
+
+ # U_EXPORT (defined in unicode/platform.h) is used to set public visibility
+ # on classes through the U_COMMON_API and U_I18N_API macros (among others).
+ # When linking against the system ICU library, we want its symbols to have
+ # public LTO visibility. This disables CFI checks for the ICU classes and
+ # allows whole-program optimization to be applied to the rest of Chromium.
+ #
+ # Both U_COMMON_API and U_I18N_API macros would be defined to U_EXPORT only
+ # when U_COMBINED_IMPLEMENTATION is defined (see unicode/utypes.h). Because
+ # we override the default system UCHAR_TYPE (char16_t), it is not possible
+ # to use U_COMBINED_IMPLEMENTATION at this moment, meaning the U_COMMON_API
+ # and U_I18N_API macros are set to U_IMPORT which is an empty definition.
+ #
+ # Until building with UCHAR_TYPE=char16_t is supported, one way to apply
+ # public visibility (and thus public LTO visibility) to all ICU classes is
+ # to define U_IMPORT to have the same value as U_EXPORT. For more details,
+ # please see: https://crbug.com/822820
+ "U_IMPORT=U_EXPORT",
]
}
--
2.16.3
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