[clang][analyzer] Fix StdLibraryFunctionsChecker 'mkdir' return value.

[balazske]

Summary

The functions 'mkdir', 'mknod', 'mkdirat', 'mknodat' return 0 on success
and -1 on failure. The checker modeled these functions with a >= 0
return value on success which is changed to 0 only. This fix makes
ErrnoChecker work better for these functions.

[steakhal]

Note in the summary that this patch affects:

• mkdir, mkdirat
• mknod, mknodat

The checker modeled these functions with a >= 0 return value on success which is incorrect.

Technically, it was correct previously. Now it's not only correct but also precise ;)

[steakhal]

This looks like a standalone patch.
Feel free to rebase to main and land it.

[balazske]

rebase

[steakhal]

It feels like the parent revision is not correct.
Land it.

clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp

if (ModelPOSIX) {
     // FIXME: Improve for errno modeling.
     addToFunctionSummaryMap(
         "getcwd", Signature(ArgTypes{CharPtrTy, SizeTy}, RetType{CharPtrTy}),
         Summary(NoEvalCall)
             .ArgConstraint(
                 ArgumentCondition(1, WithinRange, Range(0, SizeMax))));
 
     // int mkdir(const char *pathname, mode_t mode);
-    // FIXME: returns 0 on success, ReturnsValidFileDescriptor is incorrect
     addToFunctionSummaryMap(
         "mkdir", Signature(ArgTypes{ConstCharPtrTy, Mode_tTy}, RetType{IntTy}),
         Summary(NoEvalCall)
-            .Case(ReturnsValidFileDescriptor, ErrnoMustNotBeChecked)
+            .Case(ReturnsZero, ErrnoMustNotBeChecked)
             .Case(ReturnsMinusOne, ErrnoNEZeroIrrelevant)
             .ArgConstraint(NotNull(ArgNo(0))));
 
     // int mkdirat(int dirfd, const char *pathname, mode_t mode);
-    // FIXME: returns 0 on success, ReturnsValidFileDescriptor is incorrect
     addToFunctionSummaryMap(
         "mkdirat",
         Signature(ArgTypes{IntTy, ConstCharPtrTy, Mode_tTy}, RetType{IntTy}),
         Summary(NoEvalCall)
-            .Case(ReturnsValidFileDescriptor, ErrnoMustNotBeChecked)
+            .Case(ReturnsZero, ErrnoMustNotBeChecked)
             .Case(ReturnsMinusOne, ErrnoNEZeroIrrelevant)
             .ArgConstraint(NotNull(ArgNo(1))));
 
     Optional<QualType> Dev_tTy = lookupTy("dev_t");
 
     // int mknod(const char *pathname, mode_t mode, dev_t dev);
-    // FIXME: returns 0 on success, ReturnsValidFileDescriptor is incorrect
     addToFunctionSummaryMap(
         "mknod",
         Signature(ArgTypes{ConstCharPtrTy, Mode_tTy, Dev_tTy}, RetType{IntTy}),
         Summary(NoEvalCall)
-            .Case(ReturnsValidFileDescriptor, ErrnoMustNotBeChecked)
+            .Case(ReturnsZero, ErrnoMustNotBeChecked)
             .Case(ReturnsMinusOne, ErrnoNEZeroIrrelevant)
             .ArgConstraint(NotNull(ArgNo(0))));
 
     // int mknodat(int dirfd, const char *pathname, mode_t mode, dev_t dev);
-    // FIXME: returns 0 on success, ReturnsValidFileDescriptor is incorrect
     addToFunctionSummaryMap(
         "mknodat",
         Signature(ArgTypes{IntTy, ConstCharPtrTy, Mode_tTy, Dev_tTy},
                   RetType{IntTy}),
         Summary(NoEvalCall)
-            .Case(ReturnsValidFileDescriptor, ErrnoMustNotBeChecked)
+            .Case(ReturnsZero, ErrnoMustNotBeChecked)
             .Case(ReturnsMinusOne, ErrnoNEZeroIrrelevant)
             .ArgConstraint(NotNull(ArgNo(1))));
 
     // int chmod(const char *path, mode_t mode);
     addToFunctionSummaryMap(
         "chmod", Signature(ArgTypes{ConstCharPtrTy, Mode_tTy}, RetType{IntTy}),
         Summary(NoEvalCall)
             .Case(ReturnsZero, ErrnoMustNotBeChecked)