[clang] [clang][analyzer] Model more getline/getdelim pre and postconditions (PR #83027)
Alejandro Álvarez Ayllón via cfe-commits
cfe-commits at lists.llvm.org
Mon Feb 26 08:24:46 PST 2024
https://github.com/alejandro-alvarez-sonarsource updated https://github.com/llvm/llvm-project/pull/83027
>From efd1411ff7fa93a84cb3d385cb55aa411af9e9ca Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alejandro=20=C3=81lvarez=20Ayll=C3=B3n?=
<alejandro.alvarez at sonarsource.com>
Date: Wed, 21 Feb 2024 14:46:01 +0100
Subject: [PATCH] [clang][analyzer] Model getline/getdelim preconditions
1. lineptr, n and stream can not be NULL
2. if *lineptr is NULL, *n must be 0
---
.../Core/PathSensitive/CheckerHelpers.h | 6 +
.../StaticAnalyzer/Checkers/StreamChecker.cpp | 155 ++++++++-
.../StaticAnalyzer/Core/CheckerHelpers.cpp | 9 +
.../system-header-simulator-for-malloc.h | 1 +
clang/test/Analysis/getline-stream.c | 327 ++++++++++++++++++
5 files changed, 496 insertions(+), 2 deletions(-)
create mode 100644 clang/test/Analysis/getline-stream.c
diff --git a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/CheckerHelpers.h b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/CheckerHelpers.h
index 65982457ad8393..60421e5437d82f 100644
--- a/clang/include/clang/StaticAnalyzer/Core/PathSensitive/CheckerHelpers.h
+++ b/clang/include/clang/StaticAnalyzer/Core/PathSensitive/CheckerHelpers.h
@@ -13,6 +13,9 @@
#ifndef LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CHECKERHELPERS_H
#define LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CHECKERHELPERS_H
+#include "ProgramState_Fwd.h"
+#include "SVals.h"
+
#include "clang/AST/OperationKinds.h"
#include "clang/AST/Stmt.h"
#include "clang/Basic/OperatorKinds.h"
@@ -110,6 +113,9 @@ class OperatorKind {
OperatorKind operationKindFromOverloadedOperator(OverloadedOperatorKind OOK,
bool IsBinary);
+std::optional<DefinedSVal> getPointeeDefVal(SVal PtrSVal,
+ ProgramStateRef State);
+
} // namespace ento
} // namespace clang
diff --git a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
index 65bdc4cac30940..f83d4e436d0382 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp
@@ -21,6 +21,7 @@
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
+#include "llvm/ADT/ScopeExit.h"
#include "llvm/ADT/Sequence.h"
#include <functional>
#include <optional>
@@ -312,6 +313,9 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
BugType BT_StreamEof{this, "Stream already in EOF", "Stream handling error"};
BugType BT_ResourceLeak{this, "Resource leak", "Stream handling error",
/*SuppressOnSink =*/true};
+ BugType BT_SizeNull{this, "NULL size pointer", "Stream handling error"};
+ BugType BT_SizeNotZero{this, "NULL line pointer and size not zero",
+ "Stream handling error"};
public:
void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
@@ -364,10 +368,10 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
{std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, false),
std::bind(&StreamChecker::evalUngetc, _1, _2, _3, _4), 1}},
{{{"getdelim"}, 4},
- {std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, true),
+ {std::bind(&StreamChecker::preGetdelim, _1, _2, _3, _4),
std::bind(&StreamChecker::evalGetdelim, _1, _2, _3, _4), 3}},
{{{"getline"}, 3},
- {std::bind(&StreamChecker::preReadWrite, _1, _2, _3, _4, true),
+ {std::bind(&StreamChecker::preGetdelim, _1, _2, _3, _4),
std::bind(&StreamChecker::evalGetdelim, _1, _2, _3, _4), 2}},
{{{"fseek"}, 3},
{&StreamChecker::preFseek, &StreamChecker::evalFseek, 0}},
@@ -452,6 +456,9 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
void evalUngetc(const FnDescription *Desc, const CallEvent &Call,
CheckerContext &C) const;
+ void preGetdelim(const FnDescription *Desc, const CallEvent &Call,
+ CheckerContext &C) const;
+
void evalGetdelim(const FnDescription *Desc, const CallEvent &Call,
CheckerContext &C) const;
@@ -526,6 +533,14 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
ProgramStateRef ensureFseekWhenceCorrect(SVal WhenceVal, CheckerContext &C,
ProgramStateRef State) const;
+ ProgramStateRef ensurePtrNotNull(SVal PtrVal, const Expr *PtrExpr,
+ CheckerContext &C, ProgramStateRef State,
+ const StringRef PtrDescr) const;
+ ProgramStateRef
+ ensureSizeZeroIfLineNull(SVal LinePtrPtrSVal, SVal SizePtrSVal,
+ const Expr *LinePtrPtrExpr, const Expr *SizePtrExpr,
+ CheckerContext &C, ProgramStateRef State) const;
+
/// Generate warning about stream in EOF state.
/// There will be always a state transition into the passed State,
/// by the new non-fatal error node or (if failed) a normal transition,
@@ -1091,6 +1106,123 @@ void StreamChecker::evalUngetc(const FnDescription *Desc, const CallEvent &Call,
C.addTransition(StateFailed);
}
+ProgramStateRef
+StreamChecker::ensurePtrNotNull(SVal PtrVal, const Expr *PtrExpr,
+ CheckerContext &C, ProgramStateRef State,
+ const StringRef PtrDescr) const {
+ const auto Ptr = PtrVal.getAs<DefinedSVal>();
+ if (!Ptr)
+ return nullptr;
+
+ assert(PtrExpr && "Expected an argument");
+
+ const auto [PtrNotNull, PtrNull] = State->assume(*Ptr);
+ if (!PtrNotNull && PtrNull) {
+ if (ExplodedNode *N = C.generateErrorNode(PtrNull)) {
+ SmallString<256> buf;
+ llvm::raw_svector_ostream os(buf);
+ os << PtrDescr << " pointer might be NULL.";
+
+ auto R = std::make_unique<PathSensitiveBugReport>(BT_SizeNull, buf, N);
+ bugreporter::trackExpressionValue(N, PtrExpr, *R);
+ C.emitReport(std::move(R));
+ }
+ return nullptr;
+ }
+
+ return PtrNotNull;
+}
+
+ProgramStateRef StreamChecker::ensureSizeZeroIfLineNull(
+ SVal LinePtrPtrSVal, SVal SizePtrSVal, const Expr *LinePtrPtrExpr,
+ const Expr *SizePtrExpr, CheckerContext &C, ProgramStateRef State) const {
+ static constexpr char SizeNotZeroMsg[] =
+ "Line pointer might be null while n value is not zero";
+
+ // We have a pointer to a pointer to the buffer, and a pointer to the size.
+ // We want what they point at.
+ auto LinePtrSVal = getPointeeDefVal(LinePtrPtrSVal, State);
+ auto NSVal = getPointeeDefVal(SizePtrSVal, State);
+ if (!LinePtrSVal || !NSVal)
+ return nullptr;
+
+ assert(LinePtrPtrExpr &&
+ "Expected an argument with a pointer to a pointer to the buffer.");
+ assert(SizePtrExpr &&
+ "Expected an argument with a pointer to the buffer size.");
+
+ // If the line pointer is null, and n is > 0, there is UB.
+ const auto [LinePtrNotNull, LinePtrNull] = State->assume(*LinePtrSVal);
+ if (LinePtrNull && !LinePtrNotNull) {
+ const auto [NIsNotZero, NIsZero] = LinePtrNull->assume(*NSVal);
+ if (NIsNotZero && !NIsZero) {
+ if (ExplodedNode *N = C.generateErrorNode(NIsNotZero)) {
+ auto R = std::make_unique<PathSensitiveBugReport>(BT_SizeNotZero,
+ SizeNotZeroMsg, N);
+ bugreporter::trackExpressionValue(N, SizePtrExpr, *R);
+ bugreporter::trackExpressionValue(N, LinePtrPtrExpr, *R);
+ C.emitReport(std::move(R));
+ }
+ return nullptr;
+ }
+ return NIsZero;
+ }
+ return LinePtrNotNull;
+}
+
+void StreamChecker::preGetdelim(const FnDescription *Desc,
+ const CallEvent &Call,
+ CheckerContext &C) const {
+ ProgramStateRef State = C.getState();
+ SVal StreamVal = getStreamArg(Desc, Call);
+
+ auto AddTransitionOnReturn = llvm::make_scope_exit([&] {
+ if (State != nullptr) {
+ C.addTransition(State);
+ }
+ });
+
+ State = ensureStreamNonNull(StreamVal, Call.getArgExpr(Desc->StreamArgNo), C,
+ State);
+ if (!State)
+ return;
+ State = ensureStreamOpened(StreamVal, C, State);
+ if (!State)
+ return;
+ State = ensureNoFilePositionIndeterminate(StreamVal, C, State);
+ if (!State)
+ return;
+
+ // n must not be NULL
+ SVal SizePtrSval = Call.getArgSVal(1);
+ State = ensurePtrNotNull(SizePtrSval, Call.getArgExpr(1), C, State, "Size");
+ if (!State)
+ return;
+
+ // lineptr must not be NULL
+ SVal LinePtrPtrSVal = Call.getArgSVal(0);
+ State =
+ ensurePtrNotNull(LinePtrPtrSVal, Call.getArgExpr(0), C, State, "Line");
+ if (!State)
+ return;
+
+ // If lineptr points to a NULL pointer, *n must be 0
+ State =
+ ensureSizeZeroIfLineNull(LinePtrPtrSVal, SizePtrSval, Call.getArgExpr(0),
+ Call.getArgExpr(1), C, State);
+ if (!State)
+ return;
+
+ SymbolRef Sym = StreamVal.getAsSymbol();
+ if (Sym && State->get<StreamMap>(Sym)) {
+ const StreamState *SS = State->get<StreamMap>(Sym);
+ if (SS->ErrorState & ErrorFEof)
+ reportFEofWarning(Sym, C, State);
+ } else {
+ C.addTransition(State);
+ }
+}
+
void StreamChecker::evalGetdelim(const FnDescription *Desc,
const CallEvent &Call,
CheckerContext &C) const {
@@ -1116,6 +1248,20 @@ void StreamChecker::evalGetdelim(const FnDescription *Desc,
State->BindExpr(E.CE, C.getLocationContext(), RetVal);
StateNotFailed =
E.assumeBinOpNN(StateNotFailed, BO_GE, RetVal, E.getZeroVal(Call));
+ // The buffer size *n must be enough to hold the whole line, and
+ // greater than the return value, since it has to account for \0
+ auto SizePtrSval = Call.getArgSVal(1);
+ auto NVal = getPointeeDefVal(SizePtrSval, State);
+ if (NVal) {
+ StateNotFailed = StateNotFailed->assume(
+ E.SVB
+ .evalBinOp(StateNotFailed, BinaryOperator::Opcode::BO_GT, *NVal,
+ RetVal, E.SVB.getConditionType())
+ .castAs<DefinedOrUnknownSVal>(),
+ true);
+ StateNotFailed =
+ StateNotFailed->BindExpr(E.CE, C.getLocationContext(), RetVal);
+ }
if (!StateNotFailed)
return;
C.addTransition(StateNotFailed);
@@ -1129,6 +1275,11 @@ void StreamChecker::evalGetdelim(const FnDescription *Desc,
E.isStreamEof() ? ErrorFEof : ErrorFEof | ErrorFError;
StateFailed = E.setStreamState(
StateFailed, StreamState::getOpened(Desc, NewES, !NewES.isFEof()));
+ // On failure, the content of the buffer is undefined
+ if (auto NewLinePtr = getPointeeDefVal(Call.getArgSVal(0), State)) {
+ StateFailed = StateFailed->bindLoc(*NewLinePtr, UndefinedVal(),
+ C.getLocationContext());
+ }
if (E.isStreamEof())
C.addTransition(StateFailed, constructSetEofNoteTag(C, E.StreamSym));
else
diff --git a/clang/lib/StaticAnalyzer/Core/CheckerHelpers.cpp b/clang/lib/StaticAnalyzer/Core/CheckerHelpers.cpp
index 84ad20a5480792..364c87e910b7b5 100644
--- a/clang/lib/StaticAnalyzer/Core/CheckerHelpers.cpp
+++ b/clang/lib/StaticAnalyzer/Core/CheckerHelpers.cpp
@@ -14,6 +14,7 @@
#include "clang/AST/Decl.h"
#include "clang/AST/Expr.h"
#include "clang/Lex/Preprocessor.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include <optional>
namespace clang {
@@ -182,5 +183,13 @@ OperatorKind operationKindFromOverloadedOperator(OverloadedOperatorKind OOK,
}
}
+std::optional<DefinedSVal> getPointeeDefVal(SVal PtrSVal,
+ ProgramStateRef State) {
+ if (const auto *Ptr = PtrSVal.getAsRegion()) {
+ return State->getSVal(Ptr).getAs<DefinedSVal>();
+ }
+ return std::nullopt;
+}
+
} // namespace ento
} // namespace clang
diff --git a/clang/test/Analysis/Inputs/system-header-simulator-for-malloc.h b/clang/test/Analysis/Inputs/system-header-simulator-for-malloc.h
index e76455655e9e2e..bc7009eb0d1bea 100644
--- a/clang/test/Analysis/Inputs/system-header-simulator-for-malloc.h
+++ b/clang/test/Analysis/Inputs/system-header-simulator-for-malloc.h
@@ -9,6 +9,7 @@ typedef __typeof(sizeof(int)) size_t;
void *malloc(size_t);
void *calloc(size_t, size_t);
void free(void *);
+void *alloca(size_t);
#if __OBJC__
diff --git a/clang/test/Analysis/getline-stream.c b/clang/test/Analysis/getline-stream.c
new file mode 100644
index 00000000000000..b4f389e4505f73
--- /dev/null
+++ b/clang/test/Analysis/getline-stream.c
@@ -0,0 +1,327 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.unix.Stream,debug.ExprInspection -verify %s
+
+#include "Inputs/system-header-simulator.h"
+#include "Inputs/system-header-simulator-for-malloc.h"
+#include "Inputs/system-header-simulator-for-valist.h"
+
+void clang_analyzer_eval(int);
+void clang_analyzer_dump_int(int);
+extern void clang_analyzer_dump_ptr(void*);
+extern void clang_analyzer_warnIfReached();
+
+void test_getline_null_file() {
+ char *buffer = NULL;
+ size_t n = 0;
+ getline(&buffer, &n, NULL); // expected-warning {{Stream pointer might be NULL}}
+}
+
+void test_getline_null_lineptr() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+
+ char **buffer = NULL;
+ size_t n = 0;
+ getline(buffer, &n, F1); // expected-warning {{Line pointer might be NULL}}
+ fclose(F1);
+}
+
+void test_getline_null_size() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+ char *buffer = NULL;
+ getline(&buffer, NULL, F1); // expected-warning {{Size pointer might be NULL}}
+ fclose(F1);
+}
+
+void test_getline_null_buffer_bad_size() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+ char *buffer = NULL;
+ size_t n = 8;
+ getline(&buffer, &n, F1); // expected-warning {{Line pointer might be null while n value is not zero}}
+ fclose(F1);
+}
+
+void test_getline_null_buffer_bad_size_2(size_t n) {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+ char *buffer = NULL;
+ if (n > 0) {
+ getline(&buffer, &n, F1); // expected-warning {{Line pointer might be null while n value is not zero}}
+ }
+ fclose(F1);
+}
+
+void test_getline_null_buffer_unknown_size(size_t n) {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+ char *buffer = NULL;
+
+ getline(&buffer, &n, F1); // ok
+ fclose(F1);
+ free(buffer);
+}
+
+void test_getline_null_buffer() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+ char *buffer = NULL;
+ size_t n = 0;
+ ssize_t r = getline(&buffer, &n, F1);
+ // getline returns -1 on failure, number of char reads on success (>= 0)
+ if (r < -1) {
+ clang_analyzer_warnIfReached(); // must not happen
+ } else {
+ // The buffer could be allocated both on failure and success
+ clang_analyzer_dump_int(n); // expected-warning {{conj_$}}
+ clang_analyzer_dump_ptr(buffer); // expected-warning {{conj_$}}
+ }
+ free(buffer);
+ fclose(F1);
+}
+
+void test_getdelim_null_file() {
+ char *buffer = NULL;
+ size_t n = 0;
+ getdelim(&buffer, &n, '\n', NULL); // expected-warning {{Stream pointer might be NULL}}
+}
+
+void test_getdelim_null_size() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+ char *buffer = NULL;
+ getdelim(&buffer, NULL, ',', F1); // expected-warning {{Size pointer might be NULL}}
+ fclose(F1);
+}
+
+void test_getdelim_null_buffer_bad_size() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+ char *buffer = NULL;
+ size_t n = 8;
+ getdelim(&buffer, &n, ';', F1); // expected-warning {{Line pointer might be null while n value is not zero}}
+ fclose(F1);
+}
+
+void test_getdelim_null_buffer_bad_size_2(size_t n) {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+ char *buffer = NULL;
+ if (n > 0) {
+ getdelim(&buffer, &n, ' ', F1); // expected-warning {{Line pointer might be null while n value is not zero}}
+ }
+ fclose(F1);
+}
+
+void test_getdelim_null_buffer_unknown_size(size_t n) {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+ char *buffer = NULL;
+ getdelim(&buffer, &n, '-', F1); // ok
+ fclose(F1);
+ free(buffer);
+}
+
+void test_getdelim_null_buffer() {
+ FILE *F1 = tmpfile();
+ if (!F1)
+ return;
+ char *buffer = NULL;
+ size_t n = 0;
+ ssize_t r = getdelim(&buffer, &n, '\r', F1);
+ // getdelim returns -1 on failure, number of char reads on success (>= 0)
+ if (r < -1) {
+ clang_analyzer_warnIfReached(); // must not happen
+ }
+ else {
+ // The buffer could be allocated both on failure and success
+ clang_analyzer_dump_int(n); // expected-warning {{conj_$}}
+ clang_analyzer_dump_ptr(buffer); // expected-warning {{conj_$}}
+ }
+ free(buffer);
+ fclose(F1);
+}
+
+void test_getline_while() {
+ FILE *file = fopen("file.txt", "r");
+ if (file == NULL) {
+ return;
+ }
+
+ char *line = NULL;
+ size_t len = 0;
+ ssize_t read;
+
+ while ((read = getline(&line, &len, file)) != -1) {
+ printf("%s\n", line);
+ }
+
+ free(line);
+ fclose(file);
+}
+
+void test_getline_no_return_check() {
+ FILE *file = fopen("file.txt", "r");
+ if (file == NULL) {
+ return;
+ }
+
+ char *line = NULL;
+ size_t len = 0;
+ getline(&line, &len, file);
+
+ if (line[0] == '\0') {} // expected-warning {{The left operand of '==' is a garbage value}}
+
+ free(line);
+ fclose(file);
+}
+
+void test_getline_return_check() {
+ FILE *file = fopen("file.txt", "r");
+ if (file == NULL) {
+ return;
+ }
+
+ char *line = NULL;
+ size_t len = 0;
+ ssize_t r = getline(&line, &len, file);
+
+ if (r != -1) {
+ if (line[0] == '\0') {} // ok
+ }
+ free(line);
+ fclose(file);
+}
+
+void test_getline_feof_check() {
+ FILE *file = fopen("file.txt", "r");
+ if (file == NULL) {
+ return;
+ }
+
+ char *line = NULL;
+ size_t len = 0;
+ ssize_t r = getline(&line, &len, file);
+
+ if (r != -1) {
+ // success, end-of-file is not possible
+ int f = feof(file);
+ clang_analyzer_eval(f == 0); // expected-warning {{TRUE}}
+ } else {
+ // failure, end-of-file is possible, but not the only reason to fail
+ int f = feof(file);
+ clang_analyzer_eval(f == 0); // expected-warning {{TRUE}} \\
+ expected-warning {{FALSE}}
+ }
+ free(line);
+ fclose(file);
+}
+
+void test_getline_after_eof() {
+ FILE *file = fopen("file.txt", "r");
+ if (file == NULL) {
+ return;
+ }
+
+ size_t n = 10;
+ char *buffer = malloc(n);
+ ssize_t read = fread(buffer, n, 1, file);
+ if (!feof(file)) {
+ getline(&buffer, &n, file); // expected-warning {{File position of the stream might be 'indeterminate' after a failed operation. Can cause undefined behavior}}
+ }
+ fclose(file);
+ free(buffer);
+}
+
+void test_getline_feof() {
+ FILE *file = fopen("file.txt", "r");
+ if (file == NULL) {
+ return;
+ }
+
+ size_t n = 10;
+ char *buffer = malloc(n);
+ ssize_t read = fread(buffer, n, 1, file);
+ getline(&buffer, &n, file); // expected-warning {{File position of the stream might be 'indeterminate' after a failed operation. Can cause undefined behavior}} \\
+ expected-warning {{Read function called when stream is in EOF state. Function has no effect}}
+ fclose(file);
+ free(buffer);
+}
+
+void test_getline_clear_eof() {
+ FILE *file = fopen("file.txt", "r");
+ if (file == NULL) {
+ return;
+ }
+
+ size_t n = 10;
+ char *buffer = malloc(n);
+ ssize_t read = fread(buffer, n, 1, file);
+ if (feof(file)) {
+ clearerr(file);
+ getline(&buffer, &n, file); // ok
+ }
+ fclose(file);
+ free(buffer);
+}
+
+void test_getline_not_null(char **buffer, size_t *size) {
+ FILE *file = fopen("file.txt", "r");
+ if (file == NULL) {
+ return;
+ }
+
+ getline(buffer, size, file);
+ fclose(file);
+
+ if (size == NULL || buffer == NULL) {
+ clang_analyzer_warnIfReached(); // must not happen
+ }
+}
+
+void test_getline_size_0(size_t size) {
+ FILE *file = fopen("file.txt", "r");
+ if (file == NULL) {
+ return;
+ }
+
+ size_t old_size = size;
+ char *buffer = NULL;
+ ssize_t r = getline(&buffer, &size, file);
+ if (r >= 0) {
+ // Since buffer is NULL, old_size should be 0. Otherwise, there would be UB.
+ clang_analyzer_eval(old_size == 0); // expected-warning{{TRUE}}
+ }
+ fclose(file);
+ free(buffer);
+}
+
+void test_getline_ret_value() {
+ FILE *file = fopen("file.txt", "r");
+ if (file == NULL) {
+ return;
+ }
+
+ size_t n = 0;
+ char *buffer = NULL;
+ ssize_t r = getline(&buffer, &n, file);
+
+ if (r > -1) {
+ // The return value does *not* include the terminating null byte.
+ // The buffer must be large enough to include it.
+ clang_analyzer_eval(n > r); // expected-warning{{TRUE}}
+ }
+
+ fclose(file);
+ free(buffer);
+}
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