[clang] [analyzer] Assume the result of 'fopen' can't alias with 'std{in,out,err}' (PR #100085)

[Donát Nagy via cfe-commits]

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@@ -451,6 +462,10 @@ class StreamChecker : public Checker<check::PreCall, eval::Call,
   /// The built-in va_list type is platform-specific
   mutable QualType VaListType;
 
+  mutable const VarDecl *StdinDecl = nullptr;
+  mutable const VarDecl *StdoutDecl = nullptr;
+  mutable const VarDecl *StderrDecl = nullptr;
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NagyDonat wrote:

`<bikeshedding>`
In your code the three standard streams have exactly identical roles (as far as I see), and I think it would be good to emphasize this by storing them in a three-element array instead of three separate independently named variables.

For example, I could imagine a solution like 
```c++
  const char *StdStreamNames[3] = {"stdin", "stdout", "stderr"};
  mutable const VarDecl *StdStreamDecls[3] = {};
  
  // ... in checkASTDecl()
  for (int i = 0; i < 3; i++) {
    // inline getGlobalStreamPointerByName here to initialize
    // StdStreamDecls[i] via StdStreamNames[i]
  }
  
  // ... in assumeNoAliasingWithStdStreams()
  for (const VarDecl *Var : StdStreamDecls) {
    // put the definition of the lambda `assumeRetNE` here
  }
```
(This is just a rough draft, there might be more idiomatic/elegant solutions for some parts.)
`</bikeshedding>`

https://github.com/llvm/llvm-project/pull/100085