https://bugs.llvm.org/show_bug.cgi?id=45593
Bug ID: 45593
Summary: bad literal and implicit cast inserted for aarch32
unsigned long literal
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: enhancement
Priority: P
Component: C
Assignee: unassignedclangb...@nondot.org
Reporter: ndesaulni...@google.com
CC: blitzrak...@gmail.com, dgre...@apple.com,
erik.pilking...@gmail.com, kristof.be...@arm.com,
lloz...@chromium.org, llvm-bugs@lists.llvm.org,
natechancel...@gmail.com, oliver.stann...@arm.com,
richard-l...@metafoo.co.uk, srhi...@google.com
Blocks: 4068
https://godbolt.org/z/ZNBWZN is a curious case, reported by Nathan Chancellor
when looking into warning on the 5.4 LTS Linux kernel for ARCH=arm.
It seems that for
```
void foo(void) {
unsigned long bar = 0x5346434e49ul;
}
```
$ clang -Wconstant-conversion --target=arm-linux-gnueabi foo.c
<source>:2:25: warning: implicit conversion from 'unsigned long long' to
'unsigned long' changes value from 357661101641 to 1178816073
[-Wconstant-conversion]
unsigned long bar = 0x5346434e49ul;
~~~ ^~~~~~~~~~~~~~
which is unusual, and seems specific to the 32b arm target.
It seems the AST is inserting the implicit cast:
TranslationUnitDecl
`-FunctionDecl <line:1:1, line:3:1> line:1:6 foo 'void (void)'
`-CompoundStmt <col:16, line:3:1>
`-DeclStmt <line:2:5, col:39>
`-VarDecl <col:5, col:25> col:19 bar 'unsigned long' cinit
`-ImplicitCastExpr <col:25> 'unsigned long' <IntegralCast>
`-IntegerLiteral <col:25> 'unsigned long long' 357661101641
The IntegerLiteral being interpreted as 'unsigned long long' is unexpected, and
the ImplicitCastExpr to 'unsigned long' is unexpected, and triggering the
warning.
Removing the target argument shows the ImplicitCastExpr node removed, and the
IntegerLiteral interpreted as 'unsigned long' (as expected due to the `ul`
suffix). example:
TranslationUnitDecl
`-FunctionDecl <line:1:1, line:3:1> line:1:6 foo 'void (void)'
`-CompoundStmt <col:16, line:3:1>
`-DeclStmt <line:2:5, col:39>
`-VarDecl <col:5, col:25> col:19 bar 'unsigned long' cinit
`-IntegerLiteral <col:25> 'unsigned long' 357661101641
Referenced Bugs:
https://bugs.llvm.org/show_bug.cgi?id=4068
[Bug 4068] [Meta] Compiling the Linux kernel with clang
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