https://github.com/gamesh411 updated
https://github.com/llvm/llvm-project/pull/93799
From 6cc7b93783993e0e7f21124f2d640cb92484faff Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Endre=20F=C3=BCl=C3=B6p?= <endre.fu...@sigmatechnology.com>
Date: Thu, 30 May 2024 11:12:59 +0200
Subject: [PATCH 1/3] [clang][analyzer][NFC] Add test for a limitation of
alpha.unix.BlockInCriticalSection checker
Updated the documentation in `checkers.rst` to include an example of how
`trylock` function is handled.
Added a new test for a scenario where `pthread_mutex_trylock` is used,
demonstrating the current limitation.
---
clang/docs/analyzer/checkers.rst | 15 +++++++++
.../Analysis/block-in-critical-section.cpp | 31 ++++++++++++++-----
2 files changed, 39 insertions(+), 7 deletions(-)
diff --git a/clang/docs/analyzer/checkers.rst b/clang/docs/analyzer/checkers.rst
index 3a31708a1e9de..b677c5f3efa04 100644
--- a/clang/docs/analyzer/checkers.rst
+++ b/clang/docs/analyzer/checkers.rst
@@ -3148,6 +3148,21 @@ Applies to: ``lock, unlock, sleep, getc, fgets, read,
recv, pthread_mutex_lock,`
m.unlock();
}
+**Limitations**
+* The ``trylock`` and ``timedlock`` versions of acquiring locks are currently
assumed to always succeed.
+ This can lead to false positives.
+
+.. code-block:: c
+
+void trylock_example(pthread_mutex_t *m) {
+ if (pthread_mutex_trylock(m) == 0) { // assume trylock always succeeds
+ sleep(10); // warn: Call to blocking function 'sleep' inside of critical
section
+ pthread_mutex_unlock(m);
+ } else {
+ sleep(10); // false positive: Incorrect warning about blocking function
inside critical section.
+ }
+}
+
.. _alpha-unix-Chroot:
alpha.unix.Chroot (C)
diff --git a/clang/test/Analysis/block-in-critical-section.cpp
b/clang/test/Analysis/block-in-critical-section.cpp
index 87c26b9f1b520..403b7a16726a2 100644
--- a/clang/test/Analysis/block-in-critical-section.cpp
+++ b/clang/test/Analysis/block-in-critical-section.cpp
@@ -36,15 +36,15 @@ ssize_t read(int fd, void *buf, size_t count);
ssize_t recv(int sockfd, void *buf, size_t len, int flags);
struct pthread_mutex_t;
-void pthread_mutex_lock(pthread_mutex_t *mutex);
-void pthread_mutex_trylock(pthread_mutex_t *mutex);
-void pthread_mutex_unlock(pthread_mutex_t *mutex);
+int pthread_mutex_lock(pthread_mutex_t *mutex);
+int pthread_mutex_trylock(pthread_mutex_t *mutex);
+int pthread_mutex_unlock(pthread_mutex_t *mutex);
struct mtx_t;
-void mtx_lock(mtx_t *mutex);
-void mtx_timedlock(mtx_t *mutex);
-void mtx_trylock(mtx_t *mutex);
-void mtx_unlock(mtx_t *mutex);
+int mtx_lock(mtx_t *mutex);
+int mtx_timedlock(mtx_t *mutex);
+int mtx_trylock(mtx_t *mutex);
+int mtx_unlock(mtx_t *mutex);
// global params for dummy function calls
FILE *stream;
@@ -292,3 +292,20 @@ void testBlockInCriticalSectionUniqueLockNested() {
testBlockInCriticalSectionUniqueLock(); // expected-note {{Calling
'testBlockInCriticalSectionUniqueLock'}}
sleep(1); // no-warning
}
+
+void testTrylockCurrentlyFalsePositive(pthread_mutex_t *m) {
+ // expected-note@+4 {{Assuming the
condition is true}}
+ // expected-note@+3 {{Taking true
branch}}
+ // expected-note@+2 {{Assuming the
condition is false}}
+ // expected-note@+1 {{Taking false
branch}}
+ if (pthread_mutex_trylock(m) == 0) { // expected-note 2 {{Entering critical
section here}}
+ // FIXME: we are entering the critical
section only in the true branch
+ sleep(10); // expected-warning {{Call to blocking function 'sleep' inside
of critical section}}
+ // expected-note@-1 {{Call to blocking function 'sleep' inside
of critical section}}
+ pthread_mutex_unlock(m);
+ } else {
+ sleep(10); // expected-warning {{Call to blocking function 'sleep' inside
of critical section}}
+ // expected-note@-1 {{Call to blocking function 'sleep' inside
of critical section}}
+ // FIXME: this is a false positive, the lock was not acquired
+ }
+}
From 71509c4f16915483a34ad6745e555481e4a872e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Endre=20F=C3=BCl=C3=B6p?= <endre.fu...@sigmatechnology.com>
Date: Thu, 30 May 2024 14:16:12 +0200
Subject: [PATCH 2/3] fix indentation
---
clang/docs/analyzer/checkers.rst | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/clang/docs/analyzer/checkers.rst b/clang/docs/analyzer/checkers.rst
index b677c5f3efa04..5416a4d7d7f78 100644
--- a/clang/docs/analyzer/checkers.rst
+++ b/clang/docs/analyzer/checkers.rst
@@ -3154,14 +3154,14 @@ Applies to: ``lock, unlock, sleep, getc, fgets, read,
recv, pthread_mutex_lock,`
.. code-block:: c
-void trylock_example(pthread_mutex_t *m) {
- if (pthread_mutex_trylock(m) == 0) { // assume trylock always succeeds
- sleep(10); // warn: Call to blocking function 'sleep' inside of critical
section
- pthread_mutex_unlock(m);
- } else {
- sleep(10); // false positive: Incorrect warning about blocking function
inside critical section.
- }
-}
+ void trylock_example(pthread_mutex_t *m) {
+ if (pthread_mutex_trylock(m) == 0) { // assume trylock always succeeds
+ sleep(10); // warn: Call to blocking function 'sleep' inside of critical
section
+ pthread_mutex_unlock(m);
+ } else {
+ sleep(10); // false positive: Incorrect warning about blocking function
inside critical section.
+ }
+ }
.. _alpha-unix-Chroot:
From f44af12b4eda012f84354aaadc9dc26c3ccbd82f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Endre=20F=C3=BCl=C3=B6p?= <endre.fu...@sigmatechnology.com>
Date: Thu, 30 May 2024 14:34:06 +0200
Subject: [PATCH 3/3] fix missing newline
---
clang/docs/analyzer/checkers.rst | 1 +
1 file changed, 1 insertion(+)
diff --git a/clang/docs/analyzer/checkers.rst b/clang/docs/analyzer/checkers.rst
index 5416a4d7d7f78..71f8ad7d0cbc4 100644
--- a/clang/docs/analyzer/checkers.rst
+++ b/clang/docs/analyzer/checkers.rst
@@ -3149,6 +3149,7 @@ Applies to: ``lock, unlock, sleep, getc, fgets, read,
recv, pthread_mutex_lock,`
}
**Limitations**
+
* The ``trylock`` and ``timedlock`` versions of acquiring locks are currently
assumed to always succeed.
This can lead to false positives.
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