[Valgrind-developers] use of variable length arrays

[Florian K. <br...@ac...>]

A week or so ago somebody wanted to run with --num-callers=100 which did
not fly because there is a hard-wired maximum of 50. This is kind of
lame in particular in this instance where it can easily be avoided by
using a variable length array:

Index: coregrind/m_execontext.c
===================================================================
--- coregrind/m_execontext.c    (revision 12623)
+++ coregrind/m_execontext.c    (working copy)
@@ -297,7 +297,7 @@
 static ExeContext* record_ExeContext_wrk ( ThreadId tid, Word
first_ip_delta,
                                            Bool first_ip_only )
 {
-   Addr ips[VG_DEEPEST_BACKTRACE];
+   Addr ips[VG_(clo_backtrace_size)];
    UInt n_ips;

    init_ExeContext_storage();

VLAs are part of C for more than a decade now so I presume their use
should be OK (we're requiring C99 features in other places already, e.g.
mixing declarations and statements). Both gcc and clang support them.
I have a proper patch to fix the above issue but wanted to double check
first that use of VLAs is OK in valgrind.

   Florian