[clang] [clang][analyzer] Support `fflush` in the StreamChecker (PR #74296)

Ben Shi via cfe-commits cfe-commits at lists.llvm.org
Thu Dec 7 00:32:13 PST 2023


https://github.com/benshi001 updated https://github.com/llvm/llvm-project/pull/74296

>From 65ce18117f99056aafcf58151b64f4243f4d5e26 Mon Sep 17 00:00:00 2001
From: Ben Shi <bennshi at tencent.com>
Date: Mon, 4 Dec 2023 15:51:20 +0800
Subject: [PATCH 1/3] [clang][analyzer] Support `fflush` in the StreamChecker

---
 .../StaticAnalyzer/Checkers/StreamChecker.cpp    | 16 ++++++++++++++++
 .../Analysis/Inputs/system-header-simulator.h    |  1 +
 clang/test/Analysis/stream-error.c               |  9 +++++++++
 3 files changed, 26 insertions(+)

diff --git a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
index 925fc90e35543..2c725c01dc285 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
@@ -266,6 +266,7 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
        {&StreamChecker::preFseek, &StreamChecker::evalFseek, 0}},
       {{{"ftell"}, 1},
        {&StreamChecker::preDefault, &StreamChecker::evalFtell, 0}},
+      {{{"fflush"}, 1}, {&StreamChecker::preFflush, nullptr, 0}},
       {{{"rewind"}, 1},
        {&StreamChecker::preDefault, &StreamChecker::evalRewind, 0}},
       {{{"fgetpos"}, 2},
@@ -360,6 +361,9 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
                          CheckerContext &C,
                          const StreamErrorState &ErrorKind) const;
 
+  void preFflush(const FnDescription *Desc, const CallEvent &Call,
+                 CheckerContext &C) const;
+
   /// Check that the stream (in StreamVal) is not NULL.
   /// If it can only be NULL a fatal error is emitted and nullptr returned.
   /// Otherwise the return value is a new state where the stream is constrained
@@ -1191,6 +1195,18 @@ void StreamChecker::evalSetFeofFerror(const FnDescription *Desc,
   C.addTransition(State);
 }
 
+void StreamChecker::preFflush(const FnDescription *Desc, const CallEvent &Call,
+                              CheckerContext &C) const {
+  // Skip if the stream is NULL/nullptr, which means flush all streams.
+  if (!Call.getArgExpr(Desc->StreamArgNo)
+           ->isNullPointerConstant(C.getASTContext(),
+                                   Expr::NPC_ValueDependentIsNotNull)) {
+    ProgramStateRef State = C.getState();
+    if (State = ensureStreamOpened(getStreamArg(Desc, Call), C, State))
+      C.addTransition(State);
+  }
+}
+
 ProgramStateRef
 StreamChecker::ensureStreamNonNull(SVal StreamVal, const Expr *StreamE,
                                    CheckerContext &C,
diff --git a/clang/test/Analysis/Inputs/system-header-simulator.h b/clang/test/Analysis/Inputs/system-header-simulator.h
index 7089bd8bfc9d9..409a969a0d4cc 100644
--- a/clang/test/Analysis/Inputs/system-header-simulator.h
+++ b/clang/test/Analysis/Inputs/system-header-simulator.h
@@ -61,6 +61,7 @@ void clearerr(FILE *stream);
 int feof(FILE *stream);
 int ferror(FILE *stream);
 int fileno(FILE *stream);
+int fflush(FILE *stream);
 
 size_t strlen(const char *);
 
diff --git a/clang/test/Analysis/stream-error.c b/clang/test/Analysis/stream-error.c
index c8332bcbfa8ca..aa5b6be851773 100644
--- a/clang/test/Analysis/stream-error.c
+++ b/clang/test/Analysis/stream-error.c
@@ -299,6 +299,15 @@ void error_fseek_0(void) {
   fclose(F);
 }
 
+void error_fflush(void) {
+  FILE *F = tmpfile();
+  if (!F)
+    return;
+  fclose(F);
+  fflush(F);    // expected-warning {{Stream might be already closed}}
+  fflush(NULL); // no-warning
+}
+
 void error_indeterminate(void) {
   FILE *F = fopen("file", "r+");
   if (!F)

>From dcb766b468a2f29df30451f8f196d7a2371fd038 Mon Sep 17 00:00:00 2001
From: Ben Shi <bennshi at tencent.com>
Date: Wed, 6 Dec 2023 15:47:35 +0800
Subject: [PATCH 2/3] [clang][analyzer] Support `fflush` in the StreamChecker

---
 .../StaticAnalyzer/Checkers/StreamChecker.cpp | 49 ++++++++++++++++---
 clang/test/Analysis/stream-error.c            | 12 +++--
 2 files changed, 51 insertions(+), 10 deletions(-)

diff --git a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
index 2c725c01dc285..a368619fd37d2 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
@@ -266,7 +266,8 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
        {&StreamChecker::preFseek, &StreamChecker::evalFseek, 0}},
       {{{"ftell"}, 1},
        {&StreamChecker::preDefault, &StreamChecker::evalFtell, 0}},
-      {{{"fflush"}, 1}, {&StreamChecker::preFflush, nullptr, 0}},
+      {{{"fflush"}, 1},
+       {&StreamChecker::preFflush, &StreamChecker::evalFflush, 0}},
       {{{"rewind"}, 1},
        {&StreamChecker::preDefault, &StreamChecker::evalRewind, 0}},
       {{{"fgetpos"}, 2},
@@ -364,6 +365,9 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
   void preFflush(const FnDescription *Desc, const CallEvent &Call,
                  CheckerContext &C) const;
 
+  void evalFflush(const FnDescription *Desc, const CallEvent &Call,
+                  CheckerContext &C) const;
+
   /// Check that the stream (in StreamVal) is not NULL.
   /// If it can only be NULL a fatal error is emitted and nullptr returned.
   /// Otherwise the return value is a new state where the stream is constrained
@@ -1197,14 +1201,45 @@ void StreamChecker::evalSetFeofFerror(const FnDescription *Desc,
 
 void StreamChecker::preFflush(const FnDescription *Desc, const CallEvent &Call,
                               CheckerContext &C) const {
-  // Skip if the stream is NULL/nullptr, which means flush all streams.
-  if (!Call.getArgExpr(Desc->StreamArgNo)
-           ->isNullPointerConstant(C.getASTContext(),
-                                   Expr::NPC_ValueDependentIsNotNull)) {
-    ProgramStateRef State = C.getState();
-    if (State = ensureStreamOpened(getStreamArg(Desc, Call), C, State))
+  ProgramStateRef State = C.getState();
+  SVal StreamVal = getStreamArg(Desc, Call);
+  std::optional<DefinedSVal> Stream = StreamVal.getAs<DefinedSVal>();
+  if (!Stream)
+    return;
+
+  ConstraintManager::ProgramStatePair SP =
+      C.getConstraintManager().assumeDual(State, *Stream);
+  if (State = SP.first)
+    if (State = ensureStreamOpened(StreamVal, C, State))
       C.addTransition(State);
+}
+
+void StreamChecker::evalFflush(const FnDescription *Desc, const CallEvent &Call,
+                               CheckerContext &C) const {
+  ProgramStateRef State = C.getState();
+
+  // We will check the result even if the input is `NULL`,
+  // but do nothing if the input state is unknown.
+  SymbolRef StreamSym = getStreamArg(Desc, Call).getAsSymbol();
+  if (StreamSym) {
+    const StreamState *OldSS = State->get<StreamMap>(StreamSym);
+    if (!OldSS)
+      return;
+    assertStreamStateOpened(OldSS);
   }
+
+  const CallExpr *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr());
+  if (!CE)
+    return;
+
+  // `fflush` returns 0 on success, otherwise returns EOF.
+  ProgramStateRef StateNotFailed = bindInt(0, State, C, CE);
+  ProgramStateRef StateFailed = bindInt(*EofVal, State, C, CE);
+
+  // This function does not affect the stream state.
+  // Still we add success and failure state with the appropriate return value.
+  C.addTransition(StateNotFailed);
+  C.addTransition(StateFailed);
 }
 
 ProgramStateRef
diff --git a/clang/test/Analysis/stream-error.c b/clang/test/Analysis/stream-error.c
index aa5b6be851773..94787874cf839 100644
--- a/clang/test/Analysis/stream-error.c
+++ b/clang/test/Analysis/stream-error.c
@@ -301,11 +301,17 @@ void error_fseek_0(void) {
 
 void error_fflush(void) {
   FILE *F = tmpfile();
-  if (!F)
+  int Ret;
+  fflush(NULL);                      // no-warning
+  if (!F) {
+    if ((Ret = fflush(F)) != EOF)    // no-warning
+      clang_analyzer_eval(Ret == 0); // expected-warning {{TRUE}}
     return;
+  }
+  if ((Ret = fflush(F)) != 0)
+    clang_analyzer_eval(Ret == EOF); // expected-warning {{TRUE}}
   fclose(F);
-  fflush(F);    // expected-warning {{Stream might be already closed}}
-  fflush(NULL); // no-warning
+  fflush(F);                         // expected-warning {{Stream might be already closed}}
 }
 
 void error_indeterminate(void) {

>From 768fdeafb88ecac589468fd3cc3c81676534400e Mon Sep 17 00:00:00 2001
From: Ben Shi <bennshi at tencent.com>
Date: Thu, 7 Dec 2023 16:30:13 +0800
Subject: [PATCH 3/3] [clang][analyzer] Support `fflush` in the StreamChecker

---
 .../StaticAnalyzer/Checkers/StreamChecker.cpp | 58 ++++++++++++++-----
 clang/test/Analysis/stream-error.c            | 41 ++++++++++++-
 2 files changed, 85 insertions(+), 14 deletions(-)

diff --git a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
index a368619fd37d2..6e130200bc02f 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
@@ -1204,14 +1204,22 @@ void StreamChecker::preFflush(const FnDescription *Desc, const CallEvent &Call,
   ProgramStateRef State = C.getState();
   SVal StreamVal = getStreamArg(Desc, Call);
   std::optional<DefinedSVal> Stream = StreamVal.getAs<DefinedSVal>();
-  if (!Stream)
+  SymbolRef StreamSym = StreamVal.getAsSymbol();
+  if (!Stream || !StreamSym)
     return;
 
-  ConstraintManager::ProgramStatePair SP =
+  ProgramStateRef StateNotNull, StateNull;
+  std::tie(StateNotNull, StateNull) =
       C.getConstraintManager().assumeDual(State, *Stream);
-  if (State = SP.first)
-    if (State = ensureStreamOpened(StreamVal, C, State))
+  if (StateNotNull)
+    if (State = ensureStreamOpened(StreamVal, C, StateNotNull))
       C.addTransition(State);
+  if (StateNull) {
+    StateNull =
+        StateNull->set<StreamMap>(StreamSym, StreamState::getOpenFailed(Desc));
+    if (StateNull)
+      C.addTransition(StateNull);
+  }
 }
 
 void StreamChecker::evalFflush(const FnDescription *Desc, const CallEvent &Call,
@@ -1221,25 +1229,49 @@ void StreamChecker::evalFflush(const FnDescription *Desc, const CallEvent &Call,
   // We will check the result even if the input is `NULL`,
   // but do nothing if the input state is unknown.
   SymbolRef StreamSym = getStreamArg(Desc, Call).getAsSymbol();
+  const StreamState *SS;
   if (StreamSym) {
-    const StreamState *OldSS = State->get<StreamMap>(StreamSym);
-    if (!OldSS)
+    if (!(SS = State->get<StreamMap>(StreamSym)))
       return;
-    assertStreamStateOpened(OldSS);
+    assert((SS->isOpened() || SS->isOpenFailed()) &&
+           "Stream is expected to opened or open-failed");
   }
 
   const CallExpr *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr());
   if (!CE)
     return;
 
-  // `fflush` returns 0 on success, otherwise returns EOF.
-  ProgramStateRef StateNotFailed = bindInt(0, State, C, CE);
+  // `fflush` returns EOF on failure, otherwise returns 0.
   ProgramStateRef StateFailed = bindInt(*EofVal, State, C, CE);
-
-  // This function does not affect the stream state.
-  // Still we add success and failure state with the appropriate return value.
-  C.addTransition(StateNotFailed);
   C.addTransition(StateFailed);
+
+  // Clear error states if `fflush` returns 0, but retain their EOF flags.
+  ProgramStateRef StateNotFailed = bindInt(0, State, C, CE);
+  auto ClearError = [&StateNotFailed, Desc](SymbolRef Sym,
+                                            const StreamState *SS) {
+    if (SS->ErrorState & ErrorFError) {
+      StreamErrorState NewES =
+          (SS->ErrorState & ErrorFEof) ? ErrorFEof : ErrorNone;
+      StreamState NewSS = StreamState::getOpened(Desc, NewES, false);
+      StateNotFailed = StateNotFailed->set<StreamMap>(Sym, NewSS);
+    }
+  };
+
+  if (SS->isOpened()) {
+    // We only clear current stream's error state.
+    ClearError(StreamSym, SS);
+    C.addTransition(StateNotFailed);
+  } else {
+    // We clear error states for all streams.
+    const StreamMapTy &Map = StateNotFailed->get<StreamMap>();
+    for (const auto &I : Map) {
+      SymbolRef Sym = I.first;
+      const StreamState &SS = I.second;
+      if (SS.isOpened())
+        ClearError(Sym, &SS);
+    }
+    C.addTransition(StateNotFailed);
+  }
 }
 
 ProgramStateRef
diff --git a/clang/test/Analysis/stream-error.c b/clang/test/Analysis/stream-error.c
index 94787874cf839..d3dccdf092f91 100644
--- a/clang/test/Analysis/stream-error.c
+++ b/clang/test/Analysis/stream-error.c
@@ -299,7 +299,7 @@ void error_fseek_0(void) {
   fclose(F);
 }
 
-void error_fflush(void) {
+void error_fflush_0(void) {
   FILE *F = tmpfile();
   int Ret;
   fflush(NULL);                      // no-warning
@@ -314,6 +314,45 @@ void error_fflush(void) {
   fflush(F);                         // expected-warning {{Stream might be already closed}}
 }
 
+void error_fflush_1(void) {
+  FILE *F0 = tmpfile(), *F1 = tmpfile(), *F2 = tmpfile(), *F3 = tmpfile();
+  // `fflush` clears a non-EOF stream's error state.
+  if (F0) {
+    StreamTesterChecker_make_ferror_stream(F0);
+    if (fflush(F0) == 0) {             // no-warning
+      clang_analyzer_eval(ferror(F0)); // expected-warning {{FALSE}}
+      clang_analyzer_eval(feof(F0));   // expected-warning {{FALSE}}
+    }
+    fclose(F0);
+  }
+  // `fflush` clears an EOF stream's error state.
+  if (F1) {
+    StreamTesterChecker_make_ferror_stream(F1);
+    StreamTesterChecker_make_feof_stream(F1);
+    if (fflush(F1) == 0) {             // no-warning
+      clang_analyzer_eval(ferror(F1)); // expected-warning {{FALSE}}
+      clang_analyzer_eval(feof(F1));   // expected-warning {{TRUE}}
+    }
+    fclose(F1);
+  }
+  // `fflush` clears all stream's error states, while retains their EOF states.
+  if (F2 && F3) {
+    StreamTesterChecker_make_ferror_stream(F2);
+    StreamTesterChecker_make_ferror_stream(F3);
+    StreamTesterChecker_make_feof_stream(F3);
+    if (!F0 && fflush(F0) == 0) {      // no-warning
+      clang_analyzer_eval(ferror(F2)); // expected-warning {{FALSE}}
+      clang_analyzer_eval(feof(F2));   // expected-warning {{FALSE}}
+      clang_analyzer_eval(ferror(F3)); // expected-warning {{FALSE}}
+      clang_analyzer_eval(feof(F3));   // expected-warning {{TRUE}}
+    }
+  }
+  if (F2)
+    fclose(F2);
+  if (F3)
+    fclose(F3);
+}
+
 void error_indeterminate(void) {
   FILE *F = fopen("file", "r+");
   if (!F)



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