fcbc613ad8
Summary:
When using -ftrivial-auto-var-init=* options to initiate automatic
variables in a file, to disable initialization on some variables,
currently we have to manually annotate the variables with uninitialized
attribute, such as
int dont_initialize_me __attribute((uninitialized));
Making pragma clang attribute to support this attribute would make
annotating variables much easier, and could be particular useful for
bisection efforts, e.g.
void use(void*);
void buggy() {
int arr[256];
int boom;
float bam;
struct { int oops; } oops;
union { int oof; float aaaaa; } oof;
use(&arr);
use(&boom);
use(&bam);
use(&oops);
use(&oof);
}
Reviewers: jfb, rjmccall, aaron.ballman
Reviewed By: jfb, aaron.ballman
Subscribers: aaron.ballman, george.burgess.iv, dexonsmith, MaskRay, phosek, hubert.reinterpretcast, gbiv, manojgupta, llozano, srhines, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D78693
40 lines
1.3 KiB
C++
40 lines
1.3 KiB
C++
// RUN: %clang_cc1 -triple x86_64-unknown-unknown -fblocks %s -emit-llvm -o - | FileCheck %s -check-prefix=UNINIT
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// RUN: %clang_cc1 -triple x86_64-unknown-unknown -fblocks -ftrivial-auto-var-init=pattern %s -emit-llvm -o - | FileCheck %s -check-prefix=PATTERN
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// RUN: %clang_cc1 -triple x86_64-unknown-unknown -fblocks -ftrivial-auto-var-init=zero %s -emit-llvm -o - | FileCheck %s -check-prefix=ZERO
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template<typename T> void used(T &) noexcept;
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extern "C" {
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// UNINIT-LABEL: test_attribute_uninitialized(
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// UNINIT: alloca
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// UNINIT-NEXT: call void
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// ZERO-LABEL: test_attribute_uninitialized(
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// ZERO: alloca
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// ZERO-NEXT: call void
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// PATTERN-LABEL: test_attribute_uninitialized(
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// PATTERN: alloca
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// PATTERN-NEXT: call void
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void test_attribute_uninitialized() {
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[[clang::uninitialized]] int i;
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used(i);
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}
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#pragma clang attribute push([[clang::uninitialized]], apply_to = variable(is_local))
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// UNINIT-LABEL: test_pragma_attribute_uninitialized(
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// UNINIT: alloca
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// UNINIT-NEXT: call void
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// ZERO-LABEL: test_pragma_attribute_uninitialized(
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// ZERO: alloca
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// ZERO-NEXT: call void
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// PATTERN-LABEL: test_pragma_attribute_uninitialized(
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// PATTERN: alloca
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// PATTERN-NEXT: call void
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void test_pragma_attribute_uninitialized() {
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int i;
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used(i);
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}
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#pragma clang attribute pop
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} // extern "C"
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