[clang][analyzer] Support fgets in the SteamChecker
#73638
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@llvm/pr-subscribers-clang @llvm/pr-subscribers-clang-static-analyzer-1 Author: Ben Shi (benshi001) ChangesThis PR contains two commits, the first one is identical to #73335, please just review the second one about Full diff: https://github.com/llvm/llvm-project/pull/73638.diff 4 Files Affected:
diff --git a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
index 8eca989d7bcdea4..a4799b5f762caee 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
@@ -252,10 +252,16 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
std::bind(&StreamChecker::evalFreadFwrite, _1, _2, _3, _4, false), 3}},
{{{"fgetc"}, 1},
{std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, true),
- std::bind(&StreamChecker::evalFgetcFputc, _1, _2, _3, _4, true), 0}},
+ std::bind(&StreamChecker::evalFgetx, _1, _2, _3, _4, true), 0}},
+ {{{"fgets"}, 3},
+ {std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, true),
+ std::bind(&StreamChecker::evalFgetx, _1, _2, _3, _4, false), 2}},
{{{"fputc"}, 2},
{std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, false),
- std::bind(&StreamChecker::evalFgetcFputc, _1, _2, _3, _4, false), 1}},
+ std::bind(&StreamChecker::evalFputx, _1, _2, _3, _4, true), 1}},
+ {{{"fputs"}, 2},
+ {std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, false),
+ std::bind(&StreamChecker::evalFputx, _1, _2, _3, _4, false), 1}},
{{{"fseek"}, 3},
{&StreamChecker::preFseek, &StreamChecker::evalFseek, 0}},
{{{"ftell"}, 1},
@@ -317,8 +323,11 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
void evalFreadFwrite(const FnDescription *Desc, const CallEvent &Call,
CheckerContext &C, bool IsFread) const;
- void evalFgetcFputc(const FnDescription *Desc, const CallEvent &Call,
- CheckerContext &C, bool IsRead) const;
+ void evalFgetx(const FnDescription *Desc, const CallEvent &Call,
+ CheckerContext &C, bool SingleChar) const;
+
+ void evalFputx(const FnDescription *Desc, const CallEvent &Call,
+ CheckerContext &C, bool IsSingleChar) const;
void preFseek(const FnDescription *Desc, const CallEvent &Call,
CheckerContext &C) const;
@@ -754,9 +763,8 @@ void StreamChecker::evalFreadFwrite(const FnDescription *Desc,
C.addTransition(StateFailed);
}
-void StreamChecker::evalFgetcFputc(const FnDescription *Desc,
- const CallEvent &Call, CheckerContext &C,
- bool IsRead) const {
+void StreamChecker::evalFgetx(const FnDescription *Desc, const CallEvent &Call,
+ CheckerContext &C, bool SingleChar) const {
ProgramStateRef State = C.getState();
SymbolRef StreamSym = getStreamArg(Desc, Call).getAsSymbol();
if (!StreamSym)
@@ -773,10 +781,96 @@ void StreamChecker::evalFgetcFputc(const FnDescription *Desc,
assertStreamStateOpened(OldSS);
// `fgetc` returns the read character on success, otherwise returns EOF.
+ // `fgets` returns the read buffer address on success, otherwise returns NULL.
+
+ if (OldSS->ErrorState != ErrorFEof) {
+ if (SingleChar) {
+ // Generate a transition for the success state of `fgetc`.
+ NonLoc RetVal = makeRetVal(C, CE).castAs<NonLoc>();
+ ProgramStateRef StateNotFailed =
+ State->BindExpr(CE, C.getLocationContext(), RetVal);
+ SValBuilder &SVB = C.getSValBuilder();
+ ASTContext &ASTC = C.getASTContext();
+ // The returned 'unsigned char' of `fgetc` is converted to 'int',
+ // so we need to check if it is in range [0, 255].
+ auto CondLow =
+ SVB.evalBinOp(State, BO_GE, RetVal, SVB.makeZeroVal(ASTC.IntTy),
+ SVB.getConditionType())
+ .getAs<DefinedOrUnknownSVal>();
+ auto CondHigh =
+ SVB.evalBinOp(State, BO_LE, RetVal,
+ SVB.makeIntVal(SVB.getBasicValueFactory()
+ .getMaxValue(ASTC.UnsignedCharTy)
+ .getLimitedValue(),
+ ASTC.IntTy),
+ SVB.getConditionType())
+ .getAs<DefinedOrUnknownSVal>();
+ if (!CondLow || !CondHigh)
+ return;
+ StateNotFailed = StateNotFailed->assume(*CondLow, true);
+ if (!StateNotFailed)
+ return;
+ StateNotFailed = StateNotFailed->assume(*CondHigh, true);
+ if (!StateNotFailed)
+ return;
+ C.addTransition(StateNotFailed);
+ } else {
+ // Generate a transition for the success state of `fgets`.
+ std::optional<DefinedSVal> GetBuf =
+ Call.getArgSVal(0).getAs<DefinedSVal>();
+ if (!GetBuf)
+ return;
+ ProgramStateRef StateNotFailed =
+ State->BindExpr(CE, C.getLocationContext(), *GetBuf);
+ StateNotFailed = StateNotFailed->set<StreamMap>(
+ StreamSym, StreamState::getOpened(Desc));
+ C.addTransition(StateNotFailed);
+ }
+ }
+
+ // Add transition for the failed state.
+ ProgramStateRef StateFailed;
+ if (SingleChar)
+ StateFailed = bindInt(*EofVal, State, C, CE);
+ else
+ StateFailed =
+ State->BindExpr(CE, C.getLocationContext(),
+ C.getSValBuilder().makeNullWithType(CE->getType()));
+
+ // If a (non-EOF) error occurs, the resulting value of the file position
+ // indicator for the stream is indeterminate.
+ StreamErrorState NewES =
+ OldSS->ErrorState == ErrorFEof ? ErrorFEof : ErrorFEof | ErrorFError;
+ StreamState NewSS = StreamState::getOpened(Desc, NewES, !NewES.isFEof());
+ StateFailed = StateFailed->set<StreamMap>(StreamSym, NewSS);
+ if (OldSS->ErrorState != ErrorFEof)
+ C.addTransition(StateFailed, constructSetEofNoteTag(C, StreamSym));
+ else
+ C.addTransition(StateFailed);
+}
+
+void StreamChecker::evalFputx(const FnDescription *Desc, const CallEvent &Call,
+ CheckerContext &C, bool IsSingleChar) const {
+ ProgramStateRef State = C.getState();
+ SymbolRef StreamSym = getStreamArg(Desc, Call).getAsSymbol();
+ if (!StreamSym)
+ return;
+
+ const CallExpr *CE = dyn_cast_or_null<CallExpr>(Call.getOriginExpr());
+ if (!CE)
+ return;
+
+ const StreamState *OldSS = State->get<StreamMap>(StreamSym);
+ if (!OldSS)
+ return;
+
+ assertStreamStateOpened(OldSS);
+
// `fputc` returns the written character on success, otherwise returns EOF.
+ // `fputs` returns a non negative value on sucecess, otherwise returns EOF.
- // Generate a transition for the success state of fputc.
- if (!IsRead) {
+ if (IsSingleChar) {
+ // Generate a transition for the success state of `fputc`.
std::optional<NonLoc> PutVal = Call.getArgSVal(0).getAs<NonLoc>();
if (!PutVal)
return;
@@ -785,57 +879,32 @@ void StreamChecker::evalFgetcFputc(const FnDescription *Desc,
StateNotFailed =
StateNotFailed->set<StreamMap>(StreamSym, StreamState::getOpened(Desc));
C.addTransition(StateNotFailed);
- }
- // Generate a transition for the success state of fgetc.
- // If we know the state to be FEOF at fgetc, do not add a success state.
- else if (OldSS->ErrorState != ErrorFEof) {
+ } else {
+ // Generate a transition for the success state of `fputs`.
NonLoc RetVal = makeRetVal(C, CE).castAs<NonLoc>();
ProgramStateRef StateNotFailed =
State->BindExpr(CE, C.getLocationContext(), RetVal);
SValBuilder &SVB = C.getSValBuilder();
auto &ASTC = C.getASTContext();
- // The returned 'unsigned char' of `fgetc` is converted to 'int',
- // so we need to check if it is in range [0, 255].
- auto CondLow =
- SVB.evalBinOp(State, BO_GE, RetVal, SVB.makeZeroVal(ASTC.IntTy),
- SVB.getConditionType())
- .getAs<DefinedOrUnknownSVal>();
- auto CondHigh =
- SVB.evalBinOp(State, BO_LE, RetVal,
- SVB.makeIntVal(SVB.getBasicValueFactory()
- .getMaxValue(ASTC.UnsignedCharTy)
- .getLimitedValue(),
- ASTC.IntTy),
- SVB.getConditionType())
- .getAs<DefinedOrUnknownSVal>();
- if (!CondLow || !CondHigh)
+ auto Cond = SVB.evalBinOp(State, BO_GE, RetVal, SVB.makeZeroVal(ASTC.IntTy),
+ SVB.getConditionType())
+ .getAs<DefinedOrUnknownSVal>();
+ if (!Cond)
return;
- StateNotFailed = StateNotFailed->assume(*CondLow, true);
- if (!StateNotFailed)
- return;
- StateNotFailed = StateNotFailed->assume(*CondHigh, true);
+ StateNotFailed = StateNotFailed->assume(*Cond, true);
if (!StateNotFailed)
return;
+ StateNotFailed =
+ StateNotFailed->set<StreamMap>(StreamSym, StreamState::getOpened(Desc));
C.addTransition(StateNotFailed);
}
- // Add transition for the failed state.
+ // Add transition for the failed state. The resulting value of the file
+ // position indicator for the stream is indeterminate.
ProgramStateRef StateFailed = bindInt(*EofVal, State, C, CE);
-
- // If a (non-EOF) error occurs, the resulting value of the file position
- // indicator for the stream is indeterminate.
- StreamErrorState NewES;
- if (IsRead)
- NewES =
- OldSS->ErrorState == ErrorFEof ? ErrorFEof : ErrorFEof | ErrorFError;
- else
- NewES = ErrorFError;
- StreamState NewSS = StreamState::getOpened(Desc, NewES, !NewES.isFEof());
+ StreamState NewSS = StreamState::getOpened(Desc, ErrorFError, true);
StateFailed = StateFailed->set<StreamMap>(StreamSym, NewSS);
- if (IsRead && OldSS->ErrorState != ErrorFEof)
- C.addTransition(StateFailed, constructSetEofNoteTag(C, StreamSym));
- else
- C.addTransition(StateFailed);
+ C.addTransition(StateFailed);
}
void StreamChecker::preFseek(const FnDescription *Desc, const CallEvent &Call,
diff --git a/clang/test/Analysis/Inputs/system-header-simulator.h b/clang/test/Analysis/Inputs/system-header-simulator.h
index fc57e8bdc3d30c3..7089bd8bfc9d983 100644
--- a/clang/test/Analysis/Inputs/system-header-simulator.h
+++ b/clang/test/Analysis/Inputs/system-header-simulator.h
@@ -49,7 +49,9 @@ int fclose(FILE *fp);
size_t fread(void *restrict, size_t, size_t, FILE *restrict);
size_t fwrite(const void *restrict, size_t, size_t, FILE *restrict);
int fgetc(FILE *stream);
+char *fgets(char *restrict str, int count, FILE *restrict stream);
int fputc(int ch, FILE *stream);
+int fputs(const char *restrict s, FILE *restrict stream);
int fseek(FILE *__stream, long int __off, int __whence);
long int ftell(FILE *__stream);
void rewind(FILE *__stream);
diff --git a/clang/test/Analysis/stream-error.c b/clang/test/Analysis/stream-error.c
index 38e6b77b9bb5053..c8332bcbfa8ca72 100644
--- a/clang/test/Analysis/stream-error.c
+++ b/clang/test/Analysis/stream-error.c
@@ -123,6 +123,29 @@ void error_fgetc(void) {
fgetc(F); // expected-warning {{Stream might be already closed}}
}
+void error_fgets(void) {
+ FILE *F = tmpfile();
+ char Buf[256];
+ if (!F)
+ return;
+ char *Ret = fgets(Buf, sizeof(Buf), F);
+ if (Ret == Buf) {
+ clang_analyzer_eval(feof(F) || ferror(F)); // expected-warning {{FALSE}}
+ } else {
+ clang_analyzer_eval(Ret == NULL); // expected-warning {{TRUE}}
+ clang_analyzer_eval(feof(F) || ferror(F)); // expected-warning {{TRUE}}
+ if (feof(F)) {
+ clang_analyzer_eval(ferror(F)); // expected-warning {{FALSE}}
+ fgets(Buf, sizeof(Buf), F); // expected-warning {{Read function called when stream is in EOF state}}
+ } else {
+ clang_analyzer_eval(ferror(F)); // expected-warning {{TRUE}}
+ fgets(Buf, sizeof(Buf), F); // expected-warning {{might be 'indeterminate'}}
+ }
+ }
+ fclose(F);
+ fgets(Buf, sizeof(Buf), F); // expected-warning {{Stream might be already closed}}
+}
+
void error_fputc(void) {
FILE *F = tmpfile();
if (!F)
@@ -131,16 +154,50 @@ void error_fputc(void) {
if (Ret == EOF) {
clang_analyzer_eval(ferror(F)); // expected-warning {{TRUE}}
clang_analyzer_eval(feof(F)); // expected-warning {{FALSE}}
- fputc('Y', F); // expected-warning {{might be 'indeterminate'}}
+ fputc('Y', F); // expected-warning {{might be 'indeterminate'}}
} else {
- clang_analyzer_eval(Ret == 'X'); // expected-warning {{TRUE}}
- clang_analyzer_eval(feof(F) || ferror(F)); // expected-warning {{FALSE}}
- fputc('Y', F); // no-warning
+ clang_analyzer_eval(Ret == 'X'); // expected-warning {{TRUE}}
+ clang_analyzer_eval(feof(F) || ferror(F)); // expected-warning {{FALSE}}
+ fputc('Y', F); // no-warning
}
fclose(F);
fputc('A', F); // expected-warning {{Stream might be already closed}}
}
+void error_fputs(void) {
+ FILE *F = tmpfile();
+ if (!F)
+ return;
+ int Ret = fputs("XYZ", F);
+ if (Ret >= 0) {
+ clang_analyzer_eval(feof(F) || ferror(F)); // expected-warning {{FALSE}}
+ fputs("QWD", F); // no-warning
+ } else {
+ clang_analyzer_eval(Ret == EOF); // expected-warning {{TRUE}}
+ clang_analyzer_eval(ferror(F)); // expected-warning {{TRUE}}
+ clang_analyzer_eval(feof(F)); // expected-warning {{FALSE}}
+ fputs("QWD", F); // expected-warning {{might be 'indeterminate'}}
+ }
+ fclose(F);
+ fputs("ABC", F); // expected-warning {{Stream might be already closed}}
+}
+
+void write_after_eof_is_allowed(void) {
+ FILE *F = tmpfile();
+ if (!F)
+ return;
+ StreamTesterChecker_make_feof_stream(F);
+ if (fputs("QWD", F) >= 0) // no-warning
+ clang_analyzer_eval(feof(F) || ferror(F)); // expected-warning {{FALSE}}
+ StreamTesterChecker_make_feof_stream(F);
+ if (fputc('Q', F) == 'Q') // no-warning
+ clang_analyzer_eval(feof(F) || ferror(F)); // expected-warning {{FALSE}}
+ StreamTesterChecker_make_feof_stream(F);
+ if (fwrite("012345678", 1, 10, F) == 10) // no-warning
+ clang_analyzer_eval(feof(F) || ferror(F)); // expected-warning {{FALSE}}
+ fclose(F);
+}
+
void freadwrite_zerosize(FILE *F) {
size_t Ret;
Ret = fwrite(0, 1, 0, F);
diff --git a/clang/test/Analysis/stream.c b/clang/test/Analysis/stream.c
index a7ee9982478bb96..0b655dbdc571fe2 100644
--- a/clang/test/Analysis/stream.c
+++ b/clang/test/Analysis/stream.c
@@ -20,12 +20,25 @@ void check_fgetc(void) {
fclose(fp);
}
+void check_fgets(void) {
+ FILE *fp = tmpfile();
+ char buf[256];
+ fgets(buf, sizeof(buf), fp); // expected-warning {{Stream pointer might be NULL}}
+ fclose(fp);
+}
+
void check_fputc(void) {
FILE *fp = tmpfile();
fputc('A', fp); // expected-warning {{Stream pointer might be NULL}}
fclose(fp);
}
+void check_fputs(void) {
+ FILE *fp = tmpfile();
+ fputs("ABC", fp); // expected-warning {{Stream pointer might be NULL}}
+ fclose(fp);
+}
+
void check_fseek(void) {
FILE *fp = tmpfile();
fseek(fp, 0, 0); // expected-warning {{Stream pointer might be NULL}}
|
balazske
approved these changes
Nov 29, 2023
steakhal
reviewed
Jan 24, 2024
| @@ -778,42 +781,61 @@ void StreamChecker::evalFgetc(const FnDescription *Desc, const CallEvent &Call, | |||
| assertStreamStateOpened(OldSS); | |||
|
|
|||
There was a problem hiding this comment.
This patch caused a downstream test failure.
Here is the fix:
Suggested change
| // We don't model the buffer, thus they should escape. | |
| State = Call.invalidateRegions(C.blockCount(), State); |
Test where it currently breaks:
void test_double_switch_ok() {
char buffer[10] = {10};
FILE *F1 = tmpfile();
if (!F1)
return;
char* s = fgets(buffer, sizeof(buffer), F1); // ok
if (s) {
clang_analyzer_dump_char(buffer[0]); // expected-warning {{conj_$}} Should not preserve the previous value, thus should not be 10.
}
// Hmm, what do we know of the buffer on failure? IDK.
fclose(F1);
}I'd suggest to backport the fix for this to llvm-18, as this is a regression to not modeling "fgets".
There was a problem hiding this comment.
Will this invalidate only the buffer, not F1?
There was a problem hiding this comment.
At first glance you should be right. However, when I tried it, it didn't break any tests but this one.
I presume there must be something else going on that prevents escaping the stream pointer.
I've not checked.
Alternatively what I did was this:
[[nodiscard]] static ProgramStateRef
escapeArgsAfterIndex(ProgramStateRef State, CheckerContext &C,
const CallEvent &Call, unsigned FirstEscapingArgIndex) {
const auto *CE = Call.getOriginExpr();
assert(CE);
if (Call.getNumArgs() <= FirstEscapingArgIndex)
return State;
SmallVector<SVal> EscapingArgs;
EscapingArgs.reserve(Call.getNumArgs() - FirstEscapingArgIndex);
for (auto EscArgIdx :
llvm::seq<int>(FirstEscapingArgIndex, Call.getNumArgs()))
EscapingArgs.push_back(Call.getArgSVal(EscArgIdx));
State = State->invalidateRegions(EscapingArgs, CE, C.blockCount(),
C.getLocationContext(),
/*CausesPointerEscape=*/false);
return State;
}
// at the callsite:
State = escapeArgsAfterIndex(State, C, Call, /*FirstEscapingArgIndex=*/2);This approach similarly to the previous one, only broke this single test if I recall.
There was a problem hiding this comment.
There should be a same kind of problem with fread, or not? (That function was not changed in the recent commits.)
There was a problem hiding this comment.
The problem should apply to all APIs that potentially write to the passed buffer; including fread too.
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