gcc: amend __FILE__ mangling patch to only affect -fmacro-prefix-map=
THe initial intent of the change was to only affect
`-fmacro-prefix-map=` option.
Due to the bug of `if (maps == macro_prefix_maps)` condition of initial
setting all three of:
static file_prefix_map *macro_prefix_maps; /* -fmacro-prefix-map */
static file_prefix_map *debug_prefix_maps; /* -fdebug-prefix-map */
static file_prefix_map *profile_prefix_maps; /* -fprofile-prefix-map */
matches the comparison and applied the mangling (as long as on options
were passed into those before).
As a result not only (intended) `__FILE__` embedding happened in `.data`
section, but also (unintended) debugging symbols (`-fdebug-prefix-map`)
and profiling data (`-fprofile-prefix-map`) were broken by mangling.
The patch update fixes it by explicitly passing a boolean that controls
the mangling in a single call site relevant to `-fmacro-prefix-map`.
While at it fixed `int / size_t` mismatch that caused build failure on
upcoming `gcc-14`.
Tested as:
- `nix` still has no `nlohmann_json` retention
- `gdb` can now resolve `stdc++` debugging symbols in templates
- `--coverage` has working source file paths
This commit is contained in:
Sergei Trofimovich
parent
9312d7840b
commit
be41f86a80
2 changed files with 50 additions and 46 deletions
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@ -1,4 +1,4 @@
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From b10785c1be469319a09b10bc69db21159b0599ee Mon Sep 17 00:00:00 2001
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From 30908556fece379ffd7c0da96c774d8bd297e459 Mon Sep 17 00:00:00 2001
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From: Sergei Trofimovich <siarheit@google.com>
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Date: Fri, 22 Sep 2023 22:41:49 +0100
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Subject: [PATCH] gcc/file-prefix-map.cc: always mangle __FILE__ into invalid
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@ -14,9 +14,8 @@ Typical examples are `nix` -> `nlohmann_json` and `pipewire` ->
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For this reason we want to remove the occurrences of hashes in the
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expansion of `__FILE__`. `nuke-references` does it by replacing hashes
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by `eeeeee...` but those paths are also used for debug symbols. It is
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handy to be able to invert the transformation to go back to the original
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store path for debuginfod servers. The chosen solution is to make the
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by `eeeeee...`. It is handy to be able to invert the transformation to
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go back to the original store path. The chosen solution is to make the
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hash uppercase:
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- it does not trigger runtime references (except for all digit hashes,
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which are unlikely enough)
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@ -42,25 +41,27 @@ Tested as:
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...
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Mangled successfully.
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To reverse the effect of the mangle use new `NIX_GCC_DONT_MANGLE_PREFIX_MAP`
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environment variable. It should not normally be needed.
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--- a/gcc/file-prefix-map.cc
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+++ b/gcc/file-prefix-map.cc
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@@ -60,6 +60,9 @@ add_prefix_map (file_prefix_map *&maps, const char *arg, const char *opt)
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maps = map;
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}
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+/* Forward declaration for a $NIX_STORE remap hack below. */
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+static file_prefix_map *macro_prefix_maps; /* -fmacro-prefix-map */
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+
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/* Perform user-specified mapping of filename prefixes. Return the
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GC-allocated new name corresponding to FILENAME or FILENAME if no
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@@ -65,7 +65,7 @@ add_prefix_map (file_prefix_map *&maps, const char *arg, const char *opt)
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remapping was performed. */
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@@ -76,7 +79,31 @@ remap_filename (file_prefix_map *maps, const char *filename)
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static const char *
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-remap_filename (file_prefix_map *maps, const char *filename)
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+remap_filename (file_prefix_map *maps, const char *filename, bool mangle_nix_store = false)
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{
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file_prefix_map *map;
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char *s;
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@@ -76,7 +76,31 @@ remap_filename (file_prefix_map *maps, const char *filename)
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if (filename_ncmp (filename, map->old_prefix, map->old_len) == 0)
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break;
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if (!map)
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- return filename;
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+ {
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+ if (maps == macro_prefix_maps)
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+ if (mangle_nix_store && getenv("NIX_GCC_DONT_MANGLE_PREFIX_MAP") == NULL)
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+ {
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+ /* Remap the 32 characters after $NIX_STORE/ to uppercase
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+ *
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@ -76,7 +77,7 @@ Mangled successfully.
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+ {
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+ s = (char *) ggc_alloc_atomic (name_len + 1);
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+ memcpy(s, name, name_len + 1);
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+ for (int i = nix_store_len + 1; i < nix_store_len + 1 + 32; i++) {
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+ for (size_t i = nix_store_len + 1; i < nix_store_len + 1 + 32; i++) {
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+ s[i] = TOUPPER(s[i]);
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+ }
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+ return s;
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@ -87,11 +88,12 @@ Mangled successfully.
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name = filename + map->old_len;
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name_len = strlen (name) + 1;
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@@ -90,7 +117,6 @@ remap_filename (file_prefix_map *maps, const char *filename)
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ignore it in DW_AT_producer (dwarf2out.cc). */
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/* Linked lists of file_prefix_map structures. */
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-static file_prefix_map *macro_prefix_maps; /* -fmacro-prefix-map */
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static file_prefix_map *debug_prefix_maps; /* -fdebug-prefix-map */
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static file_prefix_map *profile_prefix_maps; /* -fprofile-prefix-map */
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@@ -129,7 +153,7 @@ add_profile_prefix_map (const char *arg)
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const char *
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remap_macro_filename (const char *filename)
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{
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- return remap_filename (macro_prefix_maps, filename);
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+ return remap_filename (macro_prefix_maps, filename, true);
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}
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/* Remap using -fdebug-prefix-map. Return the GC-allocated new name
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@ -1,4 +1,4 @@
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From b10785c1be469319a09b10bc69db21159b0599ee Mon Sep 17 00:00:00 2001
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From e160a8cd4a704f4b7724df02b62394f677cc4198 Mon Sep 17 00:00:00 2001
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From: Sergei Trofimovich <siarheit@google.com>
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Date: Fri, 22 Sep 2023 22:41:49 +0100
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Subject: [PATCH] gcc/file-prefix-map.cc: always mangle __FILE__ into invalid
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@ -14,9 +14,8 @@ Typical examples are `nix` -> `nlohmann_json` and `pipewire` ->
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For this reason we want to remove the occurrences of hashes in the
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expansion of `__FILE__`. `nuke-references` does it by replacing hashes
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by `eeeeee...` but those paths are also used for debug symbols. It is
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handy to be able to invert the transformation to go back to the original
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store path for debuginfod servers. The chosen solution is to make the
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by `eeeeee...`. It is handy to be able to invert the transformation to
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go back to the original store path. The chosen solution is to make the
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hash uppercase:
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- it does not trigger runtime references (except for all digit hashes,
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which are unlikely enough)
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@ -42,23 +41,25 @@ Tested as:
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...
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Mangled successfully.
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To reverse the effect of the mangle use new `NIX_GCC_DONT_MANGLE_PREFIX_MAP`
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environment variable. It should not normally be needed.
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--- a/gcc/file-prefix-map.cc
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+++ b/gcc/file-prefix-map.cc
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@@ -69,6 +69,9 @@ add_prefix_map (file_prefix_map *&maps, const char *arg, const char *opt)
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maps = map;
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}
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+/* Forward declaration for a $NIX_STORE remap hack below. */
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+static file_prefix_map *macro_prefix_maps; /* -fmacro-prefix-map */
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+
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/* Perform user-specified mapping of filename prefixes. Return the
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GC-allocated new name corresponding to FILENAME or FILENAME if no
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@@ -74,7 +74,7 @@ add_prefix_map (file_prefix_map *&maps, const char *arg, const char *opt)
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remapping was performed. */
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@@ -102,6 +105,30 @@ remap_filename (file_prefix_map *maps, const char *filename)
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static const char *
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-remap_filename (file_prefix_map *maps, const char *filename)
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+remap_filename (file_prefix_map *maps, const char *filename, bool mangle_nix_store = false)
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{
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file_prefix_map *map;
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char *s;
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@@ -102,6 +102,30 @@ remap_filename (file_prefix_map *maps, const char *filename)
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break;
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if (!map)
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{
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+ if (maps == macro_prefix_maps)
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+ if (mangle_nix_store && getenv("NIX_GCC_DONT_MANGLE_PREFIX_MAP") == NULL)
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+ {
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+ /* Remap all fo $NIX_STORE/.{32} paths to uppercase
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+ *
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@ -74,7 +75,7 @@ Mangled successfully.
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+ {
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+ s = (char *) ggc_alloc_atomic (name_len + 1);
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+ memcpy(s, name, name_len + 1);
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+ for (int i = nix_store_len + 1; i < nix_store_len + 1 + 32; i++) {
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+ for (size_t i = nix_store_len + 1; i < nix_store_len + 1 + 32; i++) {
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+ s[i] = TOUPPER(s[i]);
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+ }
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+ if (realname != filename)
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@ -85,11 +86,12 @@ Mangled successfully.
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if (realname != filename)
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free (const_cast <char *> (realname));
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return filename;
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@@ -124,7 +151,6 @@ remap_filename (file_prefix_map *maps, const char *filename)
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ignore it in DW_AT_producer (gen_command_line_string in opts.cc). */
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/* Linked lists of file_prefix_map structures. */
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-static file_prefix_map *macro_prefix_maps; /* -fmacro-prefix-map */
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static file_prefix_map *debug_prefix_maps; /* -fdebug-prefix-map */
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static file_prefix_map *profile_prefix_maps; /* -fprofile-prefix-map */
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@@ -163,7 +187,7 @@ add_profile_prefix_map (const char *arg)
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const char *
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remap_macro_filename (const char *filename)
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{
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- return remap_filename (macro_prefix_maps, filename);
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+ return remap_filename (macro_prefix_maps, filename, true);
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}
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/* Remap using -fdebug-prefix-map. Return the GC-allocated new name
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