Fix segmentation fault when .prof file not writeable

There are two ways to do retainer profiling. Quoting from the user's guide:
  1. `+RTS -hr` "Breaks down the graph by retainer set"
  2. `+RTS -hr<cc> -h<x>`, where `-h<x>` is one of normal heap profiling
     break-down options (e.g. `-hc`), and `-hr<cc> means "Restrict the
     profile to closures with retainer sets containing cost-centre
     stacks with one of the specified cost centres at the top."

Retainer profiling writes to a .hp file, like the other heap profiling
options, but also to a .prof file. Therefore, when the .prof file is not
writeable for whatever reason, retainer profiling should be turned off
completely.

This worked ok when running the program with `+RTS -hr` (option 1), but a
segfault would occur when using `+RTS -hr<cc> -h<x>`, with `x!=r` (option 2).

This commit fixes that.

Reviewed by: bgamari

Differential Revision: https://phabricator.haskell.org/D1849

GHC Trac Issues: #11489

1 files changed, 5 insertions, 0 deletions

diff --git a/rts/ProfHeap.h b/rts/ProfHeap.h
index e29a9f6974..279eef2bf9 100644
--- a/rts/ProfHeap.h
+++ b/rts/ProfHeap.h
@@ -16,6 +16,11 @@ nat     initHeapProfiling  (void);
 void    endHeapProfiling   (void);
 rtsBool strMatchesSelector (const char* str, const char* sel);
 
+#ifdef PROFILING
+// doingRetainerProfiling: `-hr` or `-hr<cc> -h<x>`
+rtsBool doingRetainerProfiling(void);
+#endif
+
 #include "EndPrivate.h"
 
 #endif /* PROFHEAP_H */