[clang] c12f30c - [clang][analyzer] Improve modeling of 'realpath' in StdLibraryFunctionsChecker (#79939)

[via cfe-commits]

Author: Ben Shi
Date: 2024-01-31T12:50:23+08:00
New Revision: c12f30c7ffedb2338d64d8f98a76ae56c497cfbb

URL: https://github.com/llvm/llvm-project/commit/c12f30c7ffedb2338d64d8f98a76ae56c497cfbb
DIFF: https://github.com/llvm/llvm-project/commit/c12f30c7ffedb2338d64d8f98a76ae56c497cfbb.diff

LOG: [clang][analyzer] Improve modeling of 'realpath' in StdLibraryFunctionsChecker (#79939)

Added: 
    

Modified: 
    clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
    clang/test/Analysis/errno-stdlibraryfunctions.c

Removed: 
    


################################################################################
diff  --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
index be26f5521c8d7..0c6293e67a86f 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
@@ -2992,12 +2992,16 @@ void StdLibraryFunctionsChecker::initFunctionSummaries(
 
     // char *realpath(const char *restrict file_name,
     //                char *restrict resolved_name);
-    // FIXME: Improve for errno modeling.
+    // FIXME: If the argument 'resolved_name' is not NULL, macro 'PATH_MAX'
+    //        should be defined in "limits.h" to guarrantee a success.
     addToFunctionSummaryMap(
         "realpath",
         Signature(ArgTypes{ConstCharPtrRestrictTy, CharPtrRestrictTy},
                   RetType{CharPtrTy}),
-        Summary(NoEvalCall).ArgConstraint(NotNull(ArgNo(0))));
+        Summary(NoEvalCall)
+            .Case({NotNull(Ret)}, ErrnoMustNotBeChecked, GenericSuccessMsg)
+            .Case({IsNull(Ret)}, ErrnoNEZeroIrrelevant, GenericFailureMsg)
+            .ArgConstraint(NotNull(ArgNo(0))));
 
     QualType CharPtrConstPtr = getPointerTy(getConstTy(CharPtrTy));
 

diff  --git a/clang/test/Analysis/errno-stdlibraryfunctions.c b/clang/test/Analysis/errno-stdlibraryfunctions.c
index 9b487fed0a2eb..a28efb764edfd 100644
--- a/clang/test/Analysis/errno-stdlibraryfunctions.c
+++ b/clang/test/Analysis/errno-stdlibraryfunctions.c
@@ -128,3 +128,13 @@ void errno_pclose(void) {
     if (errno) {} // expected-warning{{An undefined value may be read from 'errno'}}
   }
 }
+
+void errno_realpath(char *Path, char *Buf) {
+  char *Ret = realpath(Path, Buf);
+  if (!Ret) {
+    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'}}
+  }
+}