[clang] d14c631 - [analyzer][StdLibraryFunctionsChecker] Make close and mmap to accept -1 as fd

[Gabor Marton via cfe-commits]

Author: Gabor Marton
Date: 2020-12-08T16:58:30+01:00
New Revision: d14c63167315edfc4a4ad91fac9c866c6e0cb67f

URL: https://github.com/llvm/llvm-project/commit/d14c63167315edfc4a4ad91fac9c866c6e0cb67f
DIFF: https://github.com/llvm/llvm-project/commit/d14c63167315edfc4a4ad91fac9c866c6e0cb67f.diff

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

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.

Differential Revision: https://reviews.llvm.org/D92764

Added: 
    

Modified: 
    clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
index 8a34950ce7341..de825b2fee11f 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
@@ -1672,7 +1672,7 @@ void StdLibraryFunctionsChecker::initFunctionSummaries(
     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",
@@ -1734,7 +1734,7 @@ void StdLibraryFunctionsChecker::initFunctionSummaries(
         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,
@@ -1746,7 +1746,7 @@ void StdLibraryFunctionsChecker::initFunctionSummaries(
         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(