scan-build: Add support of the option --exclude like in scan-build-py

Summary:
To exclude thirdparty code.

To test:
With /tmp/foo.c
  
```
void test() {
    int x;
    x = 1; // warn
}  
```

```
$ scan-build --exclude non-existing/  --exclude /tmp/ -v gcc -c foo.c                                                                                                                                                                                   

scan-build: Using '/usr/lib/llvm-7/bin/clang' for static analysis
scan-build: Emitting reports for this run to '/tmp/scan-build-2018-09-16-214531-8410-1'.
foo.c:3:3: warning: Value stored to 'x' is never read
  x = 1; // warn
  ^   ~
1 warning generated.
scan-build: File '/tmp/foo.c' deleted: part of an ignored directory.
scan-build: 0 bugs found.
```

Reviewers: jroelofs

Reviewed By: jroelofs

Subscribers: whisperity, cfe-commits

Differential Revision: https://reviews.llvm.org/D52153

llvm-svn: 342359

clang/tools/scan-build/bin/scan-build

@@ -58,6 +58,7 @@ my %Options = (
   KeepEmpty => 0,            # Don't remove output directory even with 0 results.
   EnableCheckers => {},
   DisableCheckers => {},
+  Excludes => [],
   UseCC => undef,            # C compiler to use for compilation.
   UseCXX => undef,           # C++ compiler to use for compilation.
   AnalyzerTarget => undef,
@@ -420,6 +421,20 @@ sub ScanFile {
          # The file no longer exists: use the original path.
          $BugFile = $1;
       }
+
+      # Get just the path
+      my $p = dirname($BugFile);
+      # Check if the path is found in the list of exclude
+      if (grep { $p =~ m/$_/ } @{$Options{Excludes}}) {
+         if ($Options{Verbose}) {
+             Diag("File '$BugFile' deleted: part of an ignored directory.\n");
+         }
+
+       # File in an ignored directory. Remove it
+       unlink("$Dir/$FName");
+       return;
+      }
+
       UpdatePrefix($BugFile);
     }
     elsif (/<!-- BUGPATHLENGTH (.*) -->$/) {
@@ -1194,6 +1209,12 @@ OPTIONS:
    command. Specifying this option causes the exit status of scan-build to be 1
    if it found potential bugs and 0 otherwise.
 
+ --exclude <path>
+
+   Do not run static analyzer against files found in this
+   directory (You can specify this option multiple times).
+   Could be useful when project contains 3rd party libraries.
+
  --use-cc [compiler path]
  --use-cc=[compiler path]
 
@@ -1698,6 +1719,15 @@ sub ProcessArgs {
       next;
     }
 
+    if ($arg eq "--exclude") {
+      shift @$Args;
+      my $arg = shift @$Args;
+      # Remove the trailing slash if any
+      $arg =~ s|/$||;
+      push @{$Options{Excludes}}, $arg;
+      next;
+    }
+
     if ($arg eq "-load-plugin") {
       shift @$Args;
       push @{$Options{PluginsToLoad}}, shift @$Args;