diff options
author | Hans Wennborg <hans@hanshq.net> | 2019-02-12 08:35:38 +0000 |
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committer | Hans Wennborg <hans@hanshq.net> | 2019-02-12 08:35:38 +0000 |
commit | dc0d2a5d37f4474b828e06d2dd0198e9adb0c9df (patch) | |
tree | 0af3ca47639dfb8359fc48a1493747e943dcd5b0 | |
parent | a57d20da0ab43ad5025bb40f20195619abb0764b (diff) |
Merging r353495:
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r353495 | jfb | 2019-02-08 02:29:17 +0100 (Fri, 08 Feb 2019) | 32 lines
Variable auto-init: fix __block initialization
Summary:
Automatic initialization [1] of __block variables was trampling over the block's
headers after they'd been initialized, which caused self-init usage to crash,
such as here:
typedef struct XYZ { void (^block)(); } *xyz_t;
__attribute__((noinline))
xyz_t create(void (^block)()) {
xyz_t myself = malloc(sizeof(struct XYZ));
myself->block = block;
return myself;
}
int main() {
__block xyz_t captured = create(^(){ (void)captured; });
}
This type of code shouldn't be broken by variable auto-init, even if it's
sketchy.
[1] With -ftrivial-auto-var-init=pattern
<rdar://problem/47798396>
Reviewers: rjmccall, pcc, kcc
Subscribers: jkorous, dexonsmith, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D57797
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git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_80@353807 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r-- | lib/CodeGen/CGDecl.cpp | 10 | ||||
-rw-r--r-- | test/CodeGenCXX/trivial-auto-var-init.cpp | 26 |
2 files changed, 33 insertions, 3 deletions
diff --git a/lib/CodeGen/CGDecl.cpp b/lib/CodeGen/CGDecl.cpp index 5959d889b4..b98657ffd8 100644 --- a/lib/CodeGen/CGDecl.cpp +++ b/lib/CodeGen/CGDecl.cpp @@ -1631,11 +1631,15 @@ void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) { ? LangOptions::TrivialAutoVarInitKind::Uninitialized : getContext().getLangOpts().getTrivialAutoVarInit())); - auto initializeWhatIsTechnicallyUninitialized = [&]() { + auto initializeWhatIsTechnicallyUninitialized = [&](Address Loc) { if (trivialAutoVarInit == LangOptions::TrivialAutoVarInitKind::Uninitialized) return; + // Only initialize a __block's storage: we always initialize the header. + if (emission.IsEscapingByRef) + Loc = emitBlockByrefAddress(Loc, &D, /*follow=*/false); + CharUnits Size = getContext().getTypeSizeInChars(type); if (!Size.isZero()) { switch (trivialAutoVarInit) { @@ -1713,7 +1717,7 @@ void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) { }; if (isTrivialInitializer(Init)) { - initializeWhatIsTechnicallyUninitialized(); + initializeWhatIsTechnicallyUninitialized(Loc); return; } @@ -1727,7 +1731,7 @@ void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) { } if (!constant) { - initializeWhatIsTechnicallyUninitialized(); + initializeWhatIsTechnicallyUninitialized(Loc); LValue lv = MakeAddrLValue(Loc, type); lv.setNonGC(true); return EmitExprAsInit(Init, &D, lv, capturedByInit); diff --git a/test/CodeGenCXX/trivial-auto-var-init.cpp b/test/CodeGenCXX/trivial-auto-var-init.cpp index b795c0755b..37ff770abf 100644 --- a/test/CodeGenCXX/trivial-auto-var-init.cpp +++ b/test/CodeGenCXX/trivial-auto-var-init.cpp @@ -30,6 +30,32 @@ void test_block() { used(block); } +// Using the variable being initialized is typically UB in C, but for blocks we +// can be nice: they imply extra book-keeping and we can do the auto-init before +// any of said book-keeping. +// +// UNINIT-LABEL: test_block_self_init( +// ZERO-LABEL: test_block_self_init( +// ZERO: %block = alloca <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i8* }>, align 8 +// ZERO: %captured1 = getelementptr inbounds %struct.__block_byref_captured, %struct.__block_byref_captured* %captured, i32 0, i32 4 +// ZERO-NEXT: store %struct.XYZ* null, %struct.XYZ** %captured1, align 8 +// ZERO: %call = call %struct.XYZ* @create( +// PATTERN-LABEL: test_block_self_init( +// PATTERN: %block = alloca <{ i8*, i32, i32, i8*, %struct.__block_descriptor*, i8* }>, align 8 +// PATTERN: %captured1 = getelementptr inbounds %struct.__block_byref_captured, %struct.__block_byref_captured* %captured, i32 0, i32 4 +// PATTERN-NEXT: store %struct.XYZ* inttoptr (i64 -6148914691236517206 to %struct.XYZ*), %struct.XYZ** %captured1, align 8 +// PATTERN: %call = call %struct.XYZ* @create( +void test_block_self_init() { + using Block = void (^)(); + typedef struct XYZ { + Block block; + } * xyz_t; + extern xyz_t create(Block block); + __block xyz_t captured = create(^() { + (void)captured; + }); +} + // This type of code is currently not handled by zero / pattern initialization. // The test will break when that is fixed. // UNINIT-LABEL: test_goto_unreachable_value( |