[PATCH] Add --trace-variable=VAR as makefile debugging aid

[Luke Diamand]

Add a debugging option for reporting where a make variable is
assigned to.

Signed-off-by: Luke Diamand <address@hidden>
---
 doc/make.texi | 8 +++++++-
 main.c        | 6 ++++++
 make.1        | 3 +++
 variable.c    | 5 +++++
 variable.h    | 1 +
 5 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/doc/make.texi b/doc/make.texi
index b0f5af7..18c1429 100644
--- a/doc/make.texi
+++ b/doc/make.texi
@@ -8902,8 +8902,14 @@ imagination of @code{make}.
 Issue a warning message whenever @code{make} sees a reference to an
 undefined variable.  This can be helpful when you are trying to debug
 makefiles which use variables in complex ways.
address@hidden table
 
address@hidden address@hidden
address@hidden @code{--trace-variable}
address@hidden variables, tracing assignment
+Trace assignments to the specified variable, reporting the filename
+and line number, and the new value of the variable.
+
address@hidden table
 @node Implicit Rules, Archives, Running, Top
 @chapter Using Implicit Rules
 @cindex implicit rule
diff --git a/main.c b/main.c
index c2d4a0c..f2e07e8 100644
--- a/main.c
+++ b/main.c
@@ -280,6 +280,9 @@ int job_rfd = -1;
 
 char *sync_mutex = 0;
 
+/* Trace assignments to this variable. */
+char *trace_variable = 0;
+
 /* Maximum load average at which multiple jobs will be run.
    Negative values mean unlimited, while zero means limit to
    zero load (which could be useful to start infinite jobs remotely
@@ -418,6 +421,8 @@ static const char *const usage[] =
                               Consider FILE to be infinitely new.\n"),
     N_("\
   --warn-undefined-variables  Warn when an undefined variable is 
referenced.\n"),
+    N_("\
+  --trace-variable=VARIABLE   Trace assignments to VARIABLE\n"),
     NULL
   };
 
@@ -481,6 +486,7 @@ static const struct command_switch switches[] =
       "warn-undefined-variables" },
     { CHAR_MAX+6, strlist, &eval_strings, 1, 0, 0, 0, 0, "eval" },
     { CHAR_MAX+7, string, &sync_mutex, 1, 1, 0, 0, 0, "sync-mutex" },
+    { CHAR_MAX+8, string, &trace_variable, 1, 1, 0, 0, 0, "trace-variable" },
     { 0, 0, 0, 0, 0, 0, 0, 0, 0 }
   };
 
diff --git a/make.1 b/make.1
index ed04db9..033eacc 100644
--- a/make.1
+++ b/make.1
@@ -332,6 +332,9 @@ except that the modification time is changed only in the 
imagination of
 .TP 0.5i
 .B \-\-warn\-undefined\-variables
 Warn when an undefined variable is referenced.
+.TP 0.5i
+.B \-\-trace\-variable=VARIABLE
+Trace assignments to the given variable.
 .SH "EXIT STATUS"
 GNU
 .B make
diff --git a/variable.c b/variable.c
index 0b89d37..9e4b920 100644
--- a/variable.c
+++ b/variable.c
@@ -199,6 +199,11 @@ define_variable_in_set (const char *name, unsigned int 
length,
   struct variable **var_slot;
   struct variable var_key;
 
+  if (trace_variable &&
+      !strcmp(name, trace_variable))
+     printf (_("%s:%d: setting %s to %s\n"),
+               flocp->filenm, flocp->lineno, name, value);
+
   if (set == NULL)
     set = &global_variable_set;
 
diff --git a/variable.h b/variable.h
index fa2dbbd..a626525 100644
--- a/variable.h
+++ b/variable.h
@@ -110,6 +110,7 @@ struct pattern_var
 extern char *variable_buffer;
 extern struct variable_set_list *current_variable_set_list;
 extern struct variable *default_goal_var;
+extern char *trace_variable;
 
 /* expand.c */
 char *variable_buffer_output (char *ptr, const char *string, unsigned int 
length);
-- 
2.4.4.598.gd7bed1d