Fix a bug in Massif and Cachegrind, whereby if program's forked, the child

wrote into the parent's output file even if %p was specified.

Josef, I think Callgrind does not have this bug, but you might want to say
something about forking in the manual, as I have done for Massif and
Cachegrind.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@8154 a5019735-40e9-0310-863c-91ae7b9d1cf9

2 files changed, 23 insertions, 7 deletions

diff --git a/cachegrind/cg_main.c b/cachegrind/cg_main.c
index dcfa79c0..bd683255 100644
--- a/cachegrind/cg_main.c
+++ b/cachegrind/cg_main.c
@@ -1256,9 +1256,6 @@ static CacheCC  Dw_total;
 static BranchCC Bc_total;
 static BranchCC Bi_total;
 
-// The output file name.  Controlled by --cachegrind-out-file.
-static Char* cachegrind_out_file = NULL;
-
 static void fprint_CC_table_and_calc_totals(void)
 {
    Int     i, fd;
@@ -1266,6 +1263,14 @@ static void fprint_CC_table_and_calc_totals(void)
    Char    buf[512], *currFile = NULL, *currFn = NULL;
    LineCC* lineCC;
 
+   // Setup output filename.  Nb: it's important to do this now, ie. as late
+   // as possible.  If we do it at start-up and the program forks and the
+   // output file format string contains a %p (pid) specifier, both the
+   // parent and child will incorrectly write to the same file;  this
+   // happened in 3.3.0.
+   Char* cachegrind_out_file =
+      VG_(expand_file_name)("--cachegrind-out-file", clo_cachegrind_out_file);
+
    sres = VG_(open)(cachegrind_out_file, VKI_O_CREAT|VKI_O_TRUNC|VKI_O_WRONLY,
                                          VKI_S_IRUSR|VKI_S_IWUSR);
    if (sres.isError) {
@@ -1276,9 +1281,11 @@ static void fprint_CC_table_and_calc_totals(void)
          cachegrind_out_file );
       VG_(message)(Vg_UserMsg,
          "       ... so simulation results will be missing.");
+      VG_(free)(cachegrind_out_file);
       return;
    } else {
       fd = sres.res;
+      VG_(free)(cachegrind_out_file);
    }
 
    // "desc:" lines (giving I1/D1/L2 cache configuration).  The spaces after
@@ -1752,10 +1759,6 @@ static void cg_post_clo_init(void)
       VG_(exit)(2);
    }
 
-   // Setup output filename.
-   cachegrind_out_file =
-      VG_(expand_file_name)("--cachegrind-out-file", clo_cachegrind_out_file);
-
    CC_table =
       VG_(OSetGen_Create)(offsetof(LineCC, loc),
                           cmp_CodeLoc_LineCC,
diff --git a/cachegrind/docs/cg-manual.xml b/cachegrind/docs/cg-manual.xml
index 30857fa9..7c1764e0 100644
--- a/cachegrind/docs/cg-manual.xml
+++ b/cachegrind/docs/cg-manual.xml
@@ -820,6 +820,19 @@ way as for C/C++ programs.</para>
 
 </sect2>
 
+<sect2 id="ms-manual.forkingprograms" xreflabel="Forking Programs">
+<title>Forking Programs</title>
+<para>If your program forks, the child will inherit all the profiling data that
+has been gathered for the parent.</para>
+
+<para>If the output file format string (controlled by
+<option>--cachegrind-out-file</option>) does not contain <option>%p</option>,
+then the outputs from the parent and child will be intermingled in a single
+output file, which will almost certainly make it unreadable by
+cg_annotate.</para>
+</sect2>
+
+
 </sect1>