[clang] [clang][analyzer] Fix argument invalidations in StreamChecker. (PR #79470)

[Balazs Benics via cfe-commits]

================
@@ -0,0 +1,133 @@
+// RUN: %clang_analyze_cc1 -verify %s \
+// RUN: -analyzer-checker=core \
+// RUN: -analyzer-checker=alpha.unix.Stream \
+// RUN: -analyzer-checker=debug.StreamTester \
+// RUN: -analyzer-checker=debug.ExprInspection
+
+#include "Inputs/system-header-simulator.h"
+
+void clang_analyzer_eval(int);
+void clang_analyzer_dump(int);
+void clang_analyzer_warnIfReached(void);
+void StreamTesterChecker_make_feof_stream(FILE *);
+void StreamTesterChecker_make_ferror_stream(FILE *);
+
+void test_fread(void) {
+  FILE *F = fopen("file", "r+");
+  if (!F)
+    return;
+
+  char Buf[3] = {10, 10, 10};
+  fread(Buf, 1, 3, F);
+  // this check applies to succes and failure
+  clang_analyzer_dump(Buf[0]); // expected-warning {{conj_$}} Should not preserve the previous value, thus should not be 10.
+  clang_analyzer_dump(Buf[2]); // expected-warning {{conj_$}}
+  if (feof(F)) {
+    char Buf1[3] = {10, 10, 10};
+    fread(Buf1, 1, 3, F); // expected-warning {{is in EOF state}}
+    clang_analyzer_dump(Buf1[0]); // expected-warning {{10 S32b}}
+    clang_analyzer_dump(Buf1[2]); // expected-warning {{10 S32b}}
+  }
+
+  fclose(F);
+}
+
+void test_fwrite(void) {
+  FILE *F = fopen("file", "r+");
+  if (!F)
+    return;
+
+  char Buf[3] = {10, 10, 10};
+  fwrite(Buf, 1, 3, F);
+  // this check applies to succes and failure
+  clang_analyzer_dump(Buf[0]); // expected-warning {{10 S32b}}
+  clang_analyzer_dump(Buf[2]); // expected-warning {{10 S32b}}
+
+  fclose(F);
+}
+
+void test_fgets() {
+  FILE *F = tmpfile();
+  if (!F)
+    return;
+
+  char Buf[3] = {10, 10, 10};
+  fgets(Buf, 3, F);
+  // this check applies to succes and failure
+  clang_analyzer_dump(Buf[0]); // expected-warning {{conj_$}} Should not preserve the previous value, thus should not be 10.
+  clang_analyzer_dump(Buf[2]); // expected-warning {{conj_$}}
+  if (feof(F)) {
+    char Buf1[3] = {10, 10, 10};
+    fgets(Buf1, 3, F); // expected-warning {{is in EOF state}}
+    clang_analyzer_dump(Buf1[0]); // expected-warning {{10 S32b}}
+    clang_analyzer_dump(Buf1[2]); // expected-warning {{10 S32b}}
+  }
+
+  fclose(F);
+}
+
+void test_fputs() {
+  FILE *F = tmpfile();
+  if (!F)
+    return;
+
+  char *Buf = "aaa";
+  fputs(Buf, F);
+  // this check applies to succes and failure
+  clang_analyzer_dump(Buf[0]); // expected-warning {{97 S32b}}
+  clang_analyzer_dump(Buf[2]); // expected-warning {{97 S32b}}
+  clang_analyzer_dump(Buf[3]); // expected-warning {{0 S32b}}
+
+  fclose(F);
+}
+
+void test_fscanf() {
+  FILE *F = tmpfile();
+  if (!F)
+    return;
+
+  int a = 1;
+  unsigned b;
+  int Ret = fscanf(F, "%d %u", &a, &b);
+  if (Ret >= 0) {
+    // FIXME: return value
+    clang_analyzer_dump(a); // expected-warning {{conj_$}}
----------------
steakhal wrote:

```suggestion
    clang_analyzer_dump(a); // expected-warning {{conj_$}}
    clang_analyzer_eval(Ret > 2); // expected-warning {{FALSE}} expected-warning {{TRUE}} FIXME: should be only FALSE.
```
Let's take the opportunity for adding an expected (but failing) assumption here. May be fixed in the future.

https://github.com/llvm/llvm-project/pull/79470