[clang][analyzer] Restrict 'fopen' & 'tmpfile' modeling to POSIX vers…

…ions in StreamChecker (#70540)

'tmpfile' has only one form that it has no argument.

clang/lib/StaticAnalyzer/Checkers/StreamChecker.cpp

@@ -238,10 +238,10 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
 
 private:
   CallDescriptionMap<FnDescription> FnDescriptions = {
-      {{{"fopen"}}, {nullptr, &StreamChecker::evalFopen, ArgNone}},
+      {{{"fopen"}, 2}, {nullptr, &StreamChecker::evalFopen, ArgNone}},
       {{{"freopen"}, 3},
        {&StreamChecker::preFreopen, &StreamChecker::evalFreopen, 2}},
-      {{{"tmpfile"}}, {nullptr, &StreamChecker::evalFopen, ArgNone}},
+      {{{"tmpfile"}, 0}, {nullptr, &StreamChecker::evalFopen, ArgNone}},
       {{{"fclose"}, 1},
        {&StreamChecker::preDefault, &StreamChecker::evalFclose, 0}},
       {{{"fread"}, 4},

clang/test/Analysis/stream-non-posix-function.c

@@ -0,0 +1,16 @@
+// RUN: %clang_analyze_cc1 -fno-builtin -analyzer-checker=core,alpha.unix.Stream -verify %s
+// expected-no-diagnostics
+
+typedef struct _FILE FILE;
+
+// These functions are not standard C library functions.
+FILE *tmpfile(const char *restrict path); // Real 'tmpfile' should have exactly 0 formal parameters.
+FILE *fopen(const char *restrict path);   // Real 'fopen' should have exactly 2 formal parameters.
+
+void test_fopen_non_posix(void) {
+  FILE *fp = fopen("file"); // no-leak: This isn't the standard POSIX `fopen`, we don't know the semantics of this call.
+}
+
+void test_tmpfile_non_posix(void) {
+  FILE *fp = tmpfile("file"); // // no-leak: This isn't the standard POSIX `tmpfile`, we don't know the semantics of this call.
+}