[clang] a432358 - [-Wunsafe-buffer-usage] Add AST info to the unclaimed DRE debug notes for analysis
via cfe-commits
cfe-commits at lists.llvm.org
Fri Oct 20 14:28:58 PDT 2023
Author: ziqingluo-90
Date: 2023-10-20T14:27:14-07:00
New Revision: a4323586fcbb20f39f00d5d1bc4a94a1aeea15c4
URL: https://github.com/llvm/llvm-project/commit/a4323586fcbb20f39f00d5d1bc4a94a1aeea15c4
DIFF: https://github.com/llvm/llvm-project/commit/a4323586fcbb20f39f00d5d1bc4a94a1aeea15c4.diff
LOG: [-Wunsafe-buffer-usage] Add AST info to the unclaimed DRE debug notes for analysis
- For a better understand of what the unsupported cases are, we add
more information to the debug note---a string of ancestor AST nodes
of the unclaimed DRE. For example, an unclaimed DRE p in an
expression `*(p++)` will result in a string starting with
`DRE ==> UnaryOperator(++) ==> Paren ==> UnaryOperator(*)`.
- To find out the most common patterns of those unsupported use cases,
we add a simple script to build a prefix tree over those strings and
count each prefix. The script reads input line by line, assumes a
line is a list of words separated by `==>`s, and builds a prefix tree
over those lists.
Reviewed by: t-rasmud (Rashmi Mudduluru), NoQ (Artem Dergachev)
Differential revision: https://reviews.llvm.org/D158561
Added:
clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/lit.local.cfg
clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp
clang/utils/analyze_safe_buffer_debug_notes.py
Modified:
clang/lib/Analysis/UnsafeBufferUsage.cpp
Removed:
################################################################################
diff --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index 49cfa7c0d3e3b27..e332a3609290aac 100644
--- a/clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ b/clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -8,7 +8,9 @@
#include "clang/Analysis/Analyses/UnsafeBufferUsage.h"
#include "clang/AST/Decl.h"
+#include "clang/AST/Expr.h"
#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/AST/StmtVisitor.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/Lex/Lexer.h"
#include "clang/Lex/Preprocessor.h"
@@ -22,6 +24,52 @@ using namespace llvm;
using namespace clang;
using namespace ast_matchers;
+#ifndef NDEBUG
+namespace {
+class StmtDebugPrinter
+ : public ConstStmtVisitor<StmtDebugPrinter, std::string> {
+public:
+ std::string VisitStmt(const Stmt *S) { return S->getStmtClassName(); }
+
+ std::string VisitBinaryOperator(const BinaryOperator *BO) {
+ return "BinaryOperator(" + BO->getOpcodeStr().str() + ")";
+ }
+
+ std::string VisitUnaryOperator(const UnaryOperator *UO) {
+ return "UnaryOperator(" + UO->getOpcodeStr(UO->getOpcode()).str() + ")";
+ }
+
+ std::string VisitImplicitCastExpr(const ImplicitCastExpr *ICE) {
+ return "ImplicitCastExpr(" + std::string(ICE->getCastKindName()) + ")";
+ }
+};
+
+// Returns a string of ancestor `Stmt`s of the given `DRE` in such a form:
+// "DRE ==> parent-of-DRE ==> grandparent-of-DRE ==> ...".
+static std::string getDREAncestorString(const DeclRefExpr *DRE,
+ ASTContext &Ctx) {
+ std::stringstream SS;
+ const Stmt *St = DRE;
+ StmtDebugPrinter StmtPriner;
+
+ do {
+ SS << StmtPriner.Visit(St);
+
+ DynTypedNodeList StParents = Ctx.getParents(*St);
+
+ if (StParents.size() > 1)
+ return "unavailable due to multiple parents";
+ if (StParents.size() == 0)
+ break;
+ St = StParents.begin()->get<Stmt>();
+ if (St)
+ SS << " ==> ";
+ } while (St);
+ return SS.str();
+}
+} // namespace
+#endif /* NDEBUG */
+
namespace clang::ast_matchers {
// A `RecursiveASTVisitor` that traverses all descendants of a given node "n"
// except for those belonging to a
diff erent callable of "n".
@@ -2589,11 +2637,15 @@ void clang::checkUnsafeBufferUsage(const Decl *D,
#ifndef NDEBUG
auto AllUnclaimed = Tracker.getUnclaimedUses(it->first);
for (auto UnclaimedDRE : AllUnclaimed) {
- Handler.addDebugNoteForVar(
- it->first, UnclaimedDRE->getBeginLoc(),
- ("failed to produce fixit for '" + it->first->getNameAsString() +
- "' : has an unclaimed use"));
- }
+ std::string UnclaimedUseTrace =
+ getDREAncestorString(UnclaimedDRE, D->getASTContext());
+
+ Handler.addDebugNoteForVar(
+ it->first, UnclaimedDRE->getBeginLoc(),
+ ("failed to produce fixit for '" + it->first->getNameAsString() +
+ "' : has an unclaimed use\nThe unclaimed DRE trace: " +
+ UnclaimedUseTrace));
+ }
#endif
it = FixablesForAllVars.byVar.erase(it);
} else if (it->first->isInitCapture()) {
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/lit.local.cfg b/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/lit.local.cfg
new file mode 100644
index 000000000000000..07bac415a1a64c0
--- /dev/null
+++ b/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/lit.local.cfg
@@ -0,0 +1,11 @@
+# -*- Python -*-
+
+config.substitutions.append(
+ (
+ "%analyze_safe_buffer_debug_notes",
+ "'%s' %s" % (
+ config.python_executable,
+ os.path.join(config.clang_src_dir, "utils", "analyze_safe_buffer_debug_notes.py")
+ )
+ )
+)
diff --git a/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp b/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp
new file mode 100644
index 000000000000000..ab3d925753d4788
--- /dev/null
+++ b/clang/test/SemaCXX/warn-unsafe-buffer-usage-debug-unclaimed/warn-unsafe-buffer-usage-debug-unclaimed.cpp
@@ -0,0 +1,49 @@
+// RUN: %clang_cc1 -Wno-unused-value -Wunsafe-buffer-usage -fsafe-buffer-usage-suggestions \
+// RUN: -mllvm -debug-only=SafeBuffers \
+// RUN: -std=c++20 -verify=expected %s
+
+// RUN: %clang_cc1 -Wno-unused-value -Wunsafe-buffer-usage -fsafe-buffer-usage-suggestions \
+// RUN: -mllvm -debug-only=SafeBuffers \
+// RUN: -std=c++20 %s \
+// RUN: 2>&1 | grep 'The unclaimed DRE trace:' \
+// RUN: | sed 's/^The unclaimed DRE trace://' \
+// RUN: | %analyze_safe_buffer_debug_notes \
+// RUN: | FileCheck %s
+
+// This debugging facility is only available in debug builds.
+//
+// REQUIRES: asserts
+// REQUIRES: shell
+
+void test_unclaimed_use(int *p) { // expected-warning{{'p' is an unsafe pointer used for buffer access}}
+ p++; // expected-note{{used in pointer arithmetic here}} \
+ expected-note{{safe buffers debug: failed to produce fixit for 'p' : has an unclaimed use\n \
+ The unclaimed DRE trace: DeclRefExpr, UnaryOperator(++), CompoundStmt}}
+ *((p + 1) + 1); // expected-warning{{unsafe pointer arithmetic}} \
+ expected-note{{used in pointer arithmetic here}} \
+ expected-note{{safe buffers debug: failed to produce fixit for 'p' : has an unclaimed use\n \
+ The unclaimed DRE trace: DeclRefExpr, ImplicitCastExpr(LValueToRValue), BinaryOperator(+), ParenExpr, BinaryOperator(+), ParenExpr, UnaryOperator(*), CompoundStmt}}
+ p -= 1; // expected-note{{used in pointer arithmetic here}} \
+ expected-note{{safe buffers debug: failed to produce fixit for 'p' : has an unclaimed use\n \
+ The unclaimed DRE trace: DeclRefExpr, BinaryOperator(-=), CompoundStmt}}
+ p--; // expected-note{{used in pointer arithmetic here}} \
+ expected-note{{safe buffers debug: failed to produce fixit for 'p' : has an unclaimed use\n \
+ The unclaimed DRE trace: DeclRefExpr, UnaryOperator(--), CompoundStmt}}
+ p[5] = 5; // expected-note{{used in buffer access here}}
+}
+
+// CHECK: Root # 1
+// CHECK: |- DeclRefExpr # 4
+// CHECK: |-- UnaryOperator(++) # 1
+// CHECK: |--- CompoundStmt # 1
+// CHECK: |-- ImplicitCastExpr(LValueToRValue) # 1
+// CHECK: |--- BinaryOperator(+) # 1
+// CHECK: |---- ParenExpr # 1
+// CHECK: |----- BinaryOperator(+) # 1
+// CHECK: |------ ParenExpr # 1
+// CHECK: |------- UnaryOperator(*) # 1
+// CHECK: |-------- CompoundStmt # 1
+// CHECK: |-- BinaryOperator(-=) # 1
+// CHECK: |--- CompoundStmt # 1
+// CHECK: |-- UnaryOperator(--) # 1
+// CHECK: |--- CompoundStmt # 1
diff --git a/clang/utils/analyze_safe_buffer_debug_notes.py b/clang/utils/analyze_safe_buffer_debug_notes.py
new file mode 100644
index 000000000000000..f0a6e4de6fdbe6b
--- /dev/null
+++ b/clang/utils/analyze_safe_buffer_debug_notes.py
@@ -0,0 +1,39 @@
+import sys
+from collections import OrderedDict
+
+class Trie:
+ def __init__(self, name):
+ self.name = name
+ self.children = OrderedDict()
+ self.count = 1
+
+ def add(self, name):
+ if name in self.children:
+ self.children[name].count += 1
+ else:
+ self.children[name] = Trie(name)
+ return self.children[name]
+
+ def print(self, depth):
+ if depth > 0:
+ print('|', end="")
+ for i in range(depth):
+ print('-', end="")
+ if depth > 0:
+ print(end=" ")
+ print(self.name, '#', self.count)
+ for key, child in self.children.items():
+ child.print(depth + 1)
+
+
+Root = Trie("Root")
+
+if __name__ == "__main__":
+ for line in sys.stdin:
+ words = line.split('==>')
+ words = [word.strip() for word in words]
+ MyTrie = Root;
+ for word in words:
+ MyTrie = MyTrie.add(word)
+
+ Root.print(0)
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