[clang] [clang][analyzer] Improve 'errno' modeling of 'mkdtemp' (PR #76671)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-static-analyzer-1

Author: Ben Shi (benshi001)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/76671.diff


2 Files Affected:

- (modified) clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp (+4-2) 
- (modified) clang/test/Analysis/errno-stdlibraryfunctions.c (+24-5) 


``````````diff
diff --git a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
index 4ca49b9c0546d9..6f249b6b880283 100644
--- a/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp
@@ -2511,10 +2511,12 @@ void StdLibraryFunctionsChecker::initFunctionSummaries(
             .ArgConstraint(NotNull(ArgNo(0))));
 
     // char *mkdtemp(char *template);
-    // FIXME: Improve for errno modeling.
     addToFunctionSummaryMap(
         "mkdtemp", Signature(ArgTypes{CharPtrTy}, RetType{CharPtrTy}),
-        Summary(NoEvalCall).ArgConstraint(NotNull(ArgNo(0))));
+        Summary(NoEvalCall)
+            .Case({NotNull(Ret)}, ErrnoMustNotBeChecked, GenericSuccessMsg)
+            .Case({IsNull(Ret)}, ErrnoNEZeroIrrelevant, GenericFailureMsg)
+            .ArgConstraint(NotNull(ArgNo(0))));
 
     // char *getcwd(char *buf, size_t size);
     // FIXME: Improve for errno modeling.
diff --git a/clang/test/Analysis/errno-stdlibraryfunctions.c b/clang/test/Analysis/errno-stdlibraryfunctions.c
index dafda764af9f38..fea81fd709a8bd 100644
--- a/clang/test/Analysis/errno-stdlibraryfunctions.c
+++ b/clang/test/Analysis/errno-stdlibraryfunctions.c
@@ -7,12 +7,9 @@
 // RUN:   -analyzer-config unix.StdCLibraryFunctions:ModelPOSIX=true
 
 #include "Inputs/errno_var.h"
+#include "Inputs/std-c-library-functions-POSIX.h"
 
-typedef typeof(sizeof(int)) size_t;
-typedef __typeof(sizeof(int)) off_t;
-typedef size_t ssize_t;
-ssize_t send(int sockfd, const void *buf, size_t len, int flags);
-off_t lseek(int fildes, off_t offset, int whence);
+#define NULL ((void *) 0)
 
 void clang_analyzer_warnIfReached();
 void clang_analyzer_eval(int);
@@ -54,3 +51,25 @@ int errno_lseek(int fildes, off_t offset) {
   }
   return 0;
 }
+
+void errno_mkstemp(char *template) {
+  int FD = mkstemp(template);
+  if (FD >= 0) {
+    if (errno) {}                    // expected-warning{{An undefined value may be read from 'errno'}}
+  close(FD);
+  } else {
+    clang_analyzer_eval(FD == -1);   // expected-warning{{TRUE}}
+    clang_analyzer_eval(errno != 0); // expected-warning{{TRUE}}
+    if (errno) {}                    // no warning
+  }
+}
+
+void errno_mkdtemp(char *template) {
+  char *Dir = mkdtemp(template);
+  if (Dir == NULL) {
+    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'}}
+  }
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/76671