7d644e1215
C89 had a questionable feature where the compiler would implicitly declare a function that the user called but was never previously declared. The resulting function would be globally declared as extern int func(); -- a function without a prototype which accepts zero or more arguments. C99 removed support for this questionable feature due to severe security concerns. However, there was no deprecation period; C89 had the feature, C99 didn't. So Clang (and GCC) both supported the functionality as an extension in C99 and later modes. C2x no longer supports that function signature as it now requires all functions to have a prototype, and given the known security issues with the feature, continuing to support it as an extension is not tenable. This patch changes the diagnostic behavior for the -Wimplicit-function-declaration warning group depending on the language mode in effect. We continue to warn by default in C89 mode (due to the feature being dangerous to use). However, because this feature will not be supported in C2x mode, we've diagnosed it as being invalid for so long, the security concerns with the feature, and the trivial workaround for users (declare the function), we now default the extension warning to an error in C99-C17 mode. This still gives users an easy workaround if they are extensively using the extension in those modes (they can disable the warning or use -Wno-error to downgrade the error), but the new diagnostic makes it more clear that this feature is not supported and should be avoided. In C2x mode, we no longer allow an implicit function to be defined and treat the situation the same as any other lookup failure. Differential Revision: https://reviews.llvm.org/D122983
69 lines
3.2 KiB
C
69 lines
3.2 KiB
C
// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --function-signature --check-globals --global-value-regex "@.+"
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// RUN: %clang_cc1 -no-opaque-pointers -triple=x86_64-unknown-linux %s -emit-llvm -o - | FileCheck %s
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// This tests all kinds of hard cases with initializers and
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// array subscripts. This corresponds to PR487.
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struct X { int a[2]; };
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extern int bar();
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//.
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// CHECK: @test.i23 = internal global i32 4, align 4
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// CHECK: @i = global i32 4, align 4
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// CHECK: @Arr = global [100 x i32] zeroinitializer, align 16
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// CHECK: @foo2.X = internal global i32* bitcast (i8* getelementptr (i8, i8* bitcast ([100 x i32]* @Arr to i8*), i64 196) to i32*), align 8
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// CHECK: @foo2.i23 = internal global i32 0, align 4
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//.
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// CHECK-LABEL: define {{[^@]+}}@test
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// CHECK-SAME: () #[[ATTR0:[0-9]+]] {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: [[TMP0:%.*]] = load i32, i32* @test.i23, align 4
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// CHECK-NEXT: ret i32 [[TMP0]]
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//
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int test(void) {
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static int i23 = (int) &(((struct X *)0)->a[1]);
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return i23;
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}
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int i = (int) &( ((struct X *)0) -> a[1]);
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int Arr[100];
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// CHECK-LABEL: define {{[^@]+}}@foo
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// CHECK-SAME: (i32 noundef [[I:%.*]]) #[[ATTR0]] {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: [[I_ADDR:%.*]] = alloca i32, align 4
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// CHECK-NEXT: store i32 [[I]], i32* [[I_ADDR]], align 4
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// CHECK-NEXT: [[CALL:%.*]] = call i32 (i32*, ...) bitcast (i32 (...)* @bar to i32 (i32*, ...)*)(i32* noundef getelementptr inbounds ([100 x i32], [100 x i32]* @Arr, i64 0, i64 49))
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// CHECK-NEXT: [[TMP0:%.*]] = load i32, i32* [[I_ADDR]], align 4
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// CHECK-NEXT: [[IDXPROM:%.*]] = sext i32 [[TMP0]] to i64
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// CHECK-NEXT: [[ARRAYIDX:%.*]] = getelementptr inbounds [100 x i32], [100 x i32]* @Arr, i64 0, i64 [[IDXPROM]]
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// CHECK-NEXT: [[CALL1:%.*]] = call i32 (i32*, ...) bitcast (i32 (...)* @bar to i32 (i32*, ...)*)(i32* noundef [[ARRAYIDX]])
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// CHECK-NEXT: [[ADD:%.*]] = add nsw i32 [[CALL]], [[CALL1]]
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// CHECK-NEXT: ret i32 [[ADD]]
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//
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int foo(int i) { return bar(&Arr[49])+bar(&Arr[i]); }
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// CHECK-LABEL: define {{[^@]+}}@foo2
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// CHECK-SAME: (i32 noundef [[I:%.*]]) #[[ATTR0]] {
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// CHECK-NEXT: entry:
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// CHECK-NEXT: [[I_ADDR:%.*]] = alloca i32, align 4
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// CHECK-NEXT: [[P:%.*]] = alloca i32*, align 8
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// CHECK-NEXT: store i32 [[I]], i32* [[I_ADDR]], align 4
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// CHECK-NEXT: store i32* getelementptr inbounds ([100 x i32], [100 x i32]* @Arr, i64 0, i64 0), i32** [[P]], align 8
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// CHECK-NEXT: [[TMP0:%.*]] = load i32*, i32** [[P]], align 8
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// CHECK-NEXT: [[INCDEC_PTR:%.*]] = getelementptr inbounds i32, i32* [[TMP0]], i32 1
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// CHECK-NEXT: store i32* [[INCDEC_PTR]], i32** [[P]], align 8
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// CHECK-NEXT: [[TMP1:%.*]] = load i32, i32* [[I_ADDR]], align 4
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// CHECK-NEXT: [[IDX_EXT:%.*]] = sext i32 [[TMP1]] to i64
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// CHECK-NEXT: [[ADD_PTR:%.*]] = getelementptr inbounds i32, i32* getelementptr inbounds ([100 x i32], [100 x i32]* @Arr, i64 0, i64 0), i64 [[IDX_EXT]]
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// CHECK-NEXT: [[CALL:%.*]] = call i32 (i32*, ...) bitcast (i32 (...)* @bar to i32 (i32*, ...)*)(i32* noundef [[ADD_PTR]])
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// CHECK-NEXT: ret i32 [[CALL]]
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//
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int foo2(int i) {
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static const int *X = &Arr[49];
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static int i23 = (int) &( ((struct X *)0) -> a[0]);
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int *P = Arr;
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++P;
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return bar(Arr+i);
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}
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