Jan Engelhardt via llvm-dev
2020-Jan-21 12:19 UTC
[llvm-dev] Possible false positive on clang 9.0.1 --analyze
B::B(const S &) does aggregate-initialization with S, after which
S::cb/B::cb and lpb are initialized. clang however thinks it is still
uninitialized.
» cat x.cpp
struct S {
unsigned int cb;
unsigned char *lpb;
};
struct B : public S {
B(const S &b) : S{b.cb, nullptr}
{
if (lpb == nullptr)
;
}
};
void f(const S &x)
{
B y(x);
}
» clang++ --analyze x.cpp -v
clang version 9.0.1 [openSUSE Tumbleweed]
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib64/gcc/x86_64-suse-linux/10
Found candidate GCC installation: /usr/bin/../lib64/gcc/x86_64-suse-linux/9
Found candidate GCC installation: /usr/lib64/gcc/x86_64-suse-linux/10
Found candidate GCC installation: /usr/lib64/gcc/x86_64-suse-linux/9
Selected GCC installation: /usr/bin/../lib64/gcc/x86_64-suse-linux/10
Candidate multilib: .;@m64
Selected multilib: .;@m64
"/usr/bin/clang-9.0.1" -cc1 -triple x86_64-unknown-linux-gnu -analyze
-disable-free -disable-llvm-verifier -discard-value-names -main-file-name x.cpp
-analyzer-store=region -analyzer-opt-analyze-nested-blocks
-analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix
-analyzer-checker=deadcode -analyzer-checker=cplusplus
-analyzer-checker=security.insecureAPI.UncheckedReturn
-analyzer-checker=security.insecureAPI.getpw
-analyzer-checker=security.insecureAPI.gets
-analyzer-checker=security.insecureAPI.mktemp
-analyzer-checker=security.insecureAPI.mkstemp
-analyzer-checker=security.insecureAPI.vfork
-analyzer-checker=nullability.NullPassedToNonnull
-analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w
-mrelocation-model static -mthread-model posix -mdisable-fp-elim -fmath-errno
-masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu
x86-64 -dwarf-column-info -debugger-tuning=gdb -v -resource-dir
/usr/lib64/clang/9.0.1
-internal-isystem
/usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10
-internal-isystem
/usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/x86_64-suse-linux
-internal-isystem
/usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/backward
-internal-isystem /usr/local/include -internal-isystem
/usr/lib64/clang/9.0.1/include -internal-externc-isystem /include
-internal-externc-isystem /usr/include -fdeprecated-macro
-fdebug-compilation-dir /home/jengelh/work/kc -ferror-limit 19 -fmessage-length
0 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option
-fcolor-diagnostics -faddrsig -o x.plist -x c++ /dev/shm/x.cpp
clang -cc1 version 9.0.1 based upon LLVM 9.0.1 default target
x86_64-unknown-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10
/usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/x86_64-suse-linux
/usr/bin/../lib64/gcc/x86_64-suse-linux/10/../../../../include/c++/10/backward
/usr/local/include
/usr/lib64/clang/9.0.1/include
/usr/include
End of search list.
x.cpp:8:11: warning: The left operand of '==' is a garbage value
if (lpb == nullptr)
~~~ ^
1 warning generated.