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-Wuninitialized for struct assignment from GNU C statement expression #41949

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nickdesaulniers opened this issue Jul 12, 2019 · 5 comments
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-Wuninitialized for struct assignment from GNU C statement expression #41949

nickdesaulniers opened this issue Jul 12, 2019 · 5 comments
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@Nathan-Huckleberry
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bugzilla Issues migrated from bugzilla c duplicate Resolved as duplicate

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@nickdesaulniers
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Bugzilla Link 42604
Resolution DUPLICATE
Resolved on Jul 18, 2019 15:08
Version trunk
OS All
Blocks #31177
CC @arndb,@DougGregor,@nathanchance,@Nathan-Huckleberry,@zygoloid,@serge-sans-paille,@stephenhines

Extended Description

Consider the following example:

void init(int*);

void foo(void) {
int i = ({
init(&i);
i;
});
}

struct widget {
int x, y;
};
void init2(struct widget*);

void bar(void) {
struct widget my_widget = ({
init2(&my_widget);
my_widget;
});
}

warning: variable 'my_widget' is uninitialized when used within its own initialization [-Wuninitialized]

It seems like it's ok to do so for non-aggregate types, but aggregates issue the warning. I think it should not be a warning here?
@nickdesaulniers
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assigned to @Nathan-Huckleberry

@serge-sans-paille
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Same error, without GCC extension:

struct widget {
    int x, y;
};
void init2(struct widget*);

void bar(void) {
    struct widget my_widget = (init2(&my_widget), my_widget);
}

@zygoloid
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zygoloid mannequin commented Jul 17, 2019

These examples are undefined in C++, but valid in C; we should probably just disable this warning in C. (Without doing a significantly more sophisticated analysis, it's going to be hard to get it right.)

@nickdesaulniers
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WIP: https://reviews.llvm.org/D64678

@nickdesaulniers
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*** This bug has been marked as a duplicate of bug #31177 ***

@arndb arndb mannequin mentioned this issue Jan 31, 2017
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@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 10, 2021
This issue was closed.
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