[clang][analyzer] Improve modeling of 'fdopen' in StdLibraryFunctionsChecker

clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp

@@ -2171,6 +2171,16 @@ void StdLibraryFunctionsChecker::initFunctionSummaries(
             .ArgConstraint(NotNull(ArgNo(0)))
             .ArgConstraint(NotNull(ArgNo(1))));
 
+    // FILE *fdopen(int fd, const char *mode);
+    addToFunctionSummaryMap(
+        "fdopen",
+        Signature(ArgTypes{IntTy, ConstCharPtrTy}, RetType{FilePtrTy}),
+        Summary(NoEvalCall)
+            .Case({NotNull(Ret)}, ErrnoMustNotBeChecked, GenericSuccessMsg)
+            .Case({IsNull(Ret)}, ErrnoNEZeroIrrelevant, GenericFailureMsg)
+            .ArgConstraint(ArgumentCondition(0, WithinRange, Range(0, IntMax)))
+            .ArgConstraint(NotNull(ArgNo(1))));
+
     // FILE *tmpfile(void);
     addToFunctionSummaryMap(
         "tmpfile", Signature(ArgTypes{}, RetType{FilePtrTy}),
@@ -2853,15 +2863,6 @@ void StdLibraryFunctionsChecker::initFunctionSummaries(
         "pathconf", Signature(ArgTypes{ConstCharPtrTy, IntTy}, RetType{LongTy}),
         Summary(NoEvalCall).ArgConstraint(NotNull(ArgNo(0))));
 
-    // FILE *fdopen(int fd, const char *mode);
-    // FIXME: Improve for errno modeling.
-    addToFunctionSummaryMap(
-        "fdopen",
-        Signature(ArgTypes{IntTy, ConstCharPtrTy}, RetType{FilePtrTy}),
-        Summary(NoEvalCall)
-            .ArgConstraint(ArgumentCondition(0, WithinRange, Range(0, IntMax)))
-            .ArgConstraint(NotNull(ArgNo(1))));
-
     // void rewinddir(DIR *dir);
     addToFunctionSummaryMap(
         "rewinddir", Signature(ArgTypes{DirPtrTy}, RetType{VoidTy}),

clang/test/Analysis/std-c-library-functions-POSIX.c

@@ -17,6 +17,7 @@
 // RUN:   -triple i686-unknown-linux 2>&1 | FileCheck %s
 
 // CHECK: Loaded summary for: FILE *fopen(const char *restrict pathname, const char *restrict mode)
+// CHECK: Loaded summary for: FILE *fdopen(int fd, const char *mode)
 // CHECK: Loaded summary for: FILE *tmpfile(void)
 // CHECK: Loaded summary for: FILE *freopen(const char *restrict pathname, const char *restrict mode, FILE *restrict stream)
 // CHECK: Loaded summary for: int fclose(FILE *stream)
@@ -78,7 +79,6 @@
 // CHECK: Loaded summary for: int close(int fildes)
 // CHECK: Loaded summary for: long fpathconf(int fildes, int name)
 // CHECK: Loaded summary for: long pathconf(const char *path, int name)
-// CHECK: Loaded summary for: FILE *fdopen(int fd, const char *mode)
 // CHECK: Loaded summary for: void rewinddir(DIR *dir)
 // CHECK: Loaded summary for: void seekdir(DIR *dirp, long loc)
 // CHECK: Loaded summary for: int rand_r(unsigned int *seedp)

clang/test/Analysis/stream-errno.c

@@ -18,6 +18,16 @@ void check_fopen(void) {
   if (errno) {} // expected-warning{{An undefined value may be read from 'errno' [unix.Errno]}}
 }
 
+void check_fdopen(int Fd) {
+  FILE *F = fdopen(Fd, "r");
+  if (!F) {
+    clang_analyzer_eval(errno != 0); // expected-warning{{TRUE}}
+    if (errno) {}                    // no-warning
+  } else {
+    if (errno) {}                    // expected-warning{{An undefined value may be read from 'errno' [unix.Errno]}}
+  }
+}
+
 void check_tmpfile(void) {
   FILE *F = tmpfile();
   if (!F) {

clang/test/Analysis/stream-note.c

@@ -56,6 +56,7 @@ void check_note_freopen(void) {
 
 void check_note_fdopen(int fd) {
   FILE *F = fdopen(fd, "r"); // expected-note {{Stream opened here}}
+  // stdargs-note@-1 {{'fdopen' is successful}}
   if (!F)
     // expected-note@-1 {{'F' is non-null}}
     // expected-note@-2 {{Taking false branch}}