[analyzer][StdLibraryFunctionsChecker] Make close and mmap to accept -1 as fd

[martong]

Summary

close:
It is quite often that users chose to call close even if the fd is
negative. Theoretically, it would be nicer to close only valid fds, but
in practice the implementations of close just returns with EBADF in case
of a non-valid fd param. So, we can eliminate many false positives if we
let close to take -1 as an fd. Other negative values are very unlikely,
because open and other fd factories return with -1 in case of failure.

mmap:
In the case of MAP_ANONYMOUS flag (which is supported e.g. in Linux) the
mapping is not backed by any file; its contents are initialized to zero.
The fd argument is ignored; however, some implementations require fd to
be -1 if MAP_ANONYMOUS (or MAP_ANON) is specified, and portable
applications should ensure this.
Consequently, we must allow -1 as the 4th arg.

[steakhal]

LGTM besides my inline comment.

clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp

1737

mmap should have the same conditions, am I right?

[martong]

• Use -1 for mmap too

clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp

1737

Yep, thanks!

[steakhal]

Thank you.

clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp

if (ModelPOSIX) {
     addToFunctionSummaryMap(
         "pclose", Signature(ArgTypes{FilePtrTy}, RetType{IntTy}),
         Summary(NoEvalCall).ArgConstraint(NotNull(ArgNo(0))));
 
     // int close(int fildes);
     addToFunctionSummaryMap("close", Signature(ArgTypes{IntTy}, RetType{IntTy}),
                             Summary(NoEvalCall)
                                 .ArgConstraint(ArgumentCondition(
-                                    0, WithinRange, Range(0, IntMax))));
+                                    0, WithinRange, Range(-1, IntMax))));
 
     // long fpathconf(int fildes, int name);
     addToFunctionSummaryMap("fpathconf",
                             Signature(ArgTypes{IntTy, IntTy}, RetType{LongTy}),
                             Summary(NoEvalCall)
                                 .ArgConstraint(ArgumentCondition(
                                     0, WithinRange, Range(0, IntMax))));
 
if (ModelPOSIX) {
     // off_t offset);
     addToFunctionSummaryMap(
         "mmap",
         Signature(ArgTypes{VoidPtrTy, SizeTy, IntTy, IntTy, IntTy, Off_tTy},
                   RetType{VoidPtrTy}),
         Summary(NoEvalCall)
             .ArgConstraint(ArgumentCondition(1, WithinRange, Range(1, SizeMax)))
             .ArgConstraint(
-                ArgumentCondition(4, WithinRange, Range(0, IntMax))));
+                ArgumentCondition(4, WithinRange, Range(-1, IntMax))));
 
     Optional<QualType> Off64_tTy = lookupTy("off64_t");
     // void *mmap64(void *addr, size_t length, int prot, int flags, int fd,
     // off64_t offset);
     addToFunctionSummaryMap(
         "mmap64",
         Signature(ArgTypes{VoidPtrTy, SizeTy, IntTy, IntTy, IntTy, Off64_tTy},
                   RetType{VoidPtrTy}),
         Summary(NoEvalCall)
             .ArgConstraint(ArgumentCondition(1, WithinRange, Range(1, SizeMax)))
             .ArgConstraint(
-                ArgumentCondition(4, WithinRange, Range(0, IntMax))));
+                ArgumentCondition(4, WithinRange, Range(-1, IntMax))));
 
     // int pipe(int fildes[2]);
     addToFunctionSummaryMap(
         "pipe", Signature(ArgTypes{IntPtrTy}, RetType{IntTy}),
         Summary(NoEvalCall).ArgConstraint(NotNull(ArgNo(0))));
 
     // off_t lseek(int fildes, off_t offset, int whence);
     addToFunctionSummaryMap(