Re: [PATCH 1/4] Use SOURCE_PREFIX_MAP envvar as an implicit debug-prefix-map

[Joseph Myers]

On Wed, 2 Nov 2016, Ximin Luo wrote:

> +@item SOURCE_PREFIX_MAP If this variable is set, it specifies a mapping

The text should start on a separate line from the @item.

> +that is used to transform filepaths that are output in debug symbols.
> +This helps the embedded paths become reproducible, without having the
> +unreproducible value be visible in other input sources - such as GCC

Use a TeX em dash, ---, instead of " - ".

-- 
Joseph S. Myers
jos...@codesourcery.com

[PATCH 1/4] Use SOURCE_PREFIX_MAP envvar as an implicit debug-prefix-map

[Ximin Luo]

Define the SOURCE_PREFIX_MAP environment variable, and treat it as an implicit
CLI -fdebug-prefix-map option specified before any explicit such options.

Acknowledgements


Daniel Kahn Gillmor who wrote the patch for r231835, which saved me a lot of
time figuring out what to edit.

HW42 for discussion on the details of the proposal, and for suggesting that we
retain the ability to map the prefix to something other than ".".

ChangeLogs
--

gcc/ChangeLog:

2016-11-01  Ximin Luo  

* opts-global.c (add_debug_prefix_map_from_envvar): Add the value of
SOURCE_PREFIX_MAP as a debug_prefix_map if the former is set.
(handle_common_deferred_options): Call add_debug_prefix_map_from_envvar
before processing options.
* final.c: (add_debug_prefix_map): Be less specific in the error 
message,
since it can also be triggered by the SOURCE_PREFIX_MAP variable.
* doc/invoke.texi (Environment Variables): Document form and behaviour 
of
SOURCE_PREFIX_MAP.

gcc/testsuite/ChangeLog:

2016-11-01  Ximin Luo  

* gcc.dg/debug/dwarf2/source_prefix_map-1.c: New test.
* gcc.dg/debug/dwarf2/source_prefix_map-2.c: New test.

Index: gcc-7-20161030/gcc/opts-global.c
===
--- gcc-7-20161030.orig/gcc/opts-global.c
+++ gcc-7-20161030/gcc/opts-global.c
@@ -310,6 +310,21 @@ decode_options (struct gcc_options *opts
   finish_options (opts, opts_set, loc);
 }
 
+/* Add a debug-prefix-map using the SOURCE_PREFIX_MAP environment variable if
+   it is set.  */
+
+static void
+add_debug_prefix_map_from_envvar ()
+{
+  char *prefix_map;
+
+  prefix_map = getenv ("SOURCE_PREFIX_MAP");
+  if (!prefix_map)
+return;
+
+  add_debug_prefix_map (prefix_map);
+}
+
 /* Hold command-line options associated with stack limitation.  */
 const char *opt_fstack_limit_symbol_arg = NULL;
 int opt_fstack_limit_register_no = -1;
@@ -335,6 +350,8 @@ handle_common_deferred_options (void)
   if (flag_opt_info)
 opt_info_switch_p (NULL);
 
+  add_debug_prefix_map_from_envvar ();
+
   FOR_EACH_VEC_ELT (v, i, opt)
 {
   switch (opt->opt_index)
Index: gcc-7-20161030/gcc/final.c
===
--- gcc-7-20161030.orig/gcc/final.c
+++ gcc-7-20161030/gcc/final.c
@@ -1531,7 +1531,7 @@ add_debug_prefix_map (const char *arg)
   p = strchr (arg, '=');
   if (!p)
 {
-  error ("invalid argument %qs to -fdebug-prefix-map", arg);
+  error ("invalid value %qs for debug-prefix-map", arg);
   return;
 }
   map = XNEW (debug_prefix_map);
Index: gcc-7-20161030/gcc/doc/invoke.texi
===
--- gcc-7-20161030.orig/gcc/doc/invoke.texi
+++ gcc-7-20161030/gcc/doc/invoke.texi
@@ -26222,6 +26222,23 @@ Recognize EUCJP characters.
 If @env{LANG} is not defined, or if it has some other value, then the
 compiler uses @code{mblen} and @code{mbtowc} as defined by the default locale 
to
 recognize and translate multibyte characters.
+
+@item SOURCE_PREFIX_MAP If this variable is set, it specifies a mapping
+that is used to transform filepaths that are output in debug symbols.
+This helps the embedded paths become reproducible, without having the
+unreproducible value be visible in other input sources - such as GCC
+command-line flags or standardised build-time environment variables like
+@code{CFLAGS} - that are commonly legitimately-embedded in the build
+output by higher-level build processes.
+
+The form and behaviour is similar to @option{-fdebug-prefix-map}. That
+is, the value of @env{SOURCE_PREFIX_MAP} must be of the form
+@samp{@var{old}=@var{new}}. The split occurs on the first @code{=}
+character, so that @var{old} cannot itself contain a @code{=}.
+
+Whenever an absolute source- or build-related filepath is to be emitted
+in a final end-result output, GCC will replace @var{old} with @var{new}
+if that filepath starts with @var{old}.
 @end table
 
 @noindent
Index: gcc-7-20161030/gcc/testsuite/gcc.dg/debug/dwarf2/source_prefix_map-1.c
===
--- /dev/null
+++ gcc-7-20161030/gcc/testsuite/gcc.dg/debug/dwarf2/source_prefix_map-1.c
@@ -0,0 +1,9 @@
+/* DW_AT_comp_dir should be relative if SOURCE_PREFIX_MAP is a prefix of it. */
+/* { dg-do compile } */
+/* { dg-options "-gdwarf -dA" } */
+/* { dg-set-compiler-env-var SOURCE_PREFIX_MAP "[file dirname 
[pwd]]=DWARF2TEST" } */
+/* { dg-final { scan-assembler-dem "DW_AT_comp_dir: \"DWARF2TEST/gcc" } } */
+
+void func (void)
+{
+}
Index: gcc-7-20161030/gcc/testsuite/gcc.dg/debug/dwarf2/source_prefix_map-2.c
===
--- /dev/null
+++ gcc-7-20161030/gcc/testsuite/gcc.dg/debug/dwarf2/source_prefix_map-2.c
@@ -0,0 +1,8 @@
+/* DW_AT_comp_dir should be absolute if SOURCE_PREFIX_MAP is not