[PATCH] Add -fuse-ld= to specify an arbitrary executable as the linker
Fangrui Song
maskray@google.com
Tue May 19 19:21:44 GMT 2020
On 2020-04-06, Martin Liška wrote:
>On 4/6/20 12:32 AM, Fangrui Song wrote:
>>On 2020-03-11, Martin Liška wrote:
>>>On 2/10/20 1:02 AM, Fangrui Song via gcc-patches wrote:
>>>
>>>Hello.
>>>
>>>Thank you for the patch. You haven't received a review because we are right now
>>>in stage4 of the development cycle:
>>>https://gcc.gnu.org/develop.html#stage4
>>
>>Thanks for the review!
>>According to https://gcc.gnu.org/pipermail/gcc-patches/2020-April/543028.html "GCC 10.0 Status Report (2020-04-01)",
>>I guess GCC is not open for a new development cycle yet.
>
>Yes, it's not opened, but I expect to be opened in 3 weeks from now.
>
>>I will just answer a few questions instead of uploading a new patch.
>
>Sure, but don't hesitate to send a patch. It can sit here and wait for next stage1 ;)
Thank you! I got around and updated the patch.
Tested locally with -fuse-ld=~/Stable/bin/ld.lld and -fuse-ld=~/Dev/binutils-gdb/Debug/ld/ld-new
>>
>>>Anyway, I'm going to provide a review (even though I'm not maintainer of that).
>>>
>>>Can you please describe your test-case why you need such option? When using
>>>a different ld, I typically export PATH=/path/to/binutils and then run configure
>>>and make.
>>
>>I would hope -fuse-ld=ld.bfd and -fuse-ld=ld.gold were used instead of
>>-fuse-ld=bfd and -fuse-ld=gold, then it would be more natural to have
>>-fuse-ld=/abs/path/to/ld . https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55470
>
>Well, problem with that is that the option values are used and we want to preserve
>backward compatibility of options (if possible). I mean we can't just rename
>-fuse-ld=bfd to -fuse-ld=ld.bfd.
>
>>
>>-fuse-ld=bfd, -fuse-ld=gold and -fuse-ld=lld are hard-coded in numerous
>>places. It is too late to change that.
>>
>>One idea is to make
>>
>>-fuse-ld=bfd
>>-fuse-ld=gold
>>-fuse-ld=lld
>>
>>special. For any other value, e.g. -fuse-ld=foo or -fuse-ld=/abs/path, just searches the
>>executable named "foo" (instead of "ld.foo") or /abs/path .
>
>Yes, that seems feasible to me.
>
>>
>>Does the scheme sound good? If it is agreed, I can make a similar change to clang.
>
>Yes, please send a patch and we can make another round of review process.
>
>Thanks,
>Martin
>
>>
>>>I noticed not ideal error message:
>>>
>>>$ gcc -fuse-ld=pes /tmp/foo.c
>>>collect2: fatal error: cannot find ‘ld’
>>>compilation terminated.
>>>
>>>while clang prints:
>>>
>>>$clang -fuse-ld=pes /tmp/foo.c
>>>clang-9.0: error: invalid linker name in argument '-fuse-ld=pes'
>>>
>>>The rest of the patch is comment inline...
>>
>>Thanks for all the comments.
>>
>>>> PR driver/93645
>>>> * common.opt (-fuse-ld=): Delete -fuse-ld=[bfd|gold|lld]. Add -fuse-ld=.
>>>> * opts.c (common_handle_option): Handle OPT_fuse_ld_.
>>>> * gcc.c (driver_handle_option): Likewise.
>>>> * collect2.c (main): Likewise.
>>>>---
>>>> gcc/ChangeLog | 8 ++++++
>>>> gcc/collect2.c | 67 ++++++++++++++++++++++++---------------------
>>>> gcc/common.opt | 14 ++--------
>>>> gcc/doc/invoke.texi | 15 +++-------
>>>> gcc/gcc.c | 14 ++++------
>>>> gcc/opts.c | 4 +--
>>>> 6 files changed, 57 insertions(+), 65 deletions(-)
>>>>
>>>>diff --git a/gcc/ChangeLog b/gcc/ChangeLog
>>>>index feb2d066d0b..6bcec12d841 100644
>>>>--- a/gcc/ChangeLog
>>>>+++ b/gcc/ChangeLog
>>>>@@ -1,3 +1,11 @@
>>>>+2020-02-09 Fangrui Song <maskray@google.com>
>>>>+
>>>>+ PR driver/93645
>>>>+ * common.opt (-fuse-ld=): Delete -fuse-ld=[bfd|gold|lld]. Add -fuse-ld=.
>>>>+ * opts.c (common_handle_option): Handle OPT_fuse_ld_.
>>>>+ * gcc.c (driver_handle_option): Likewise.
>>>>+ * collect2.c (main): Likewise.
>>>>+
>>>> 2020-02-09 Uroš Bizjak <ubizjak@gmail.com>
>>>> * recog.c: Move pass_split_before_sched2 code in front of
>>>>diff --git a/gcc/collect2.c b/gcc/collect2.c
>>>>index 502d629141c..a3ef525a93b 100644
>>>>--- a/gcc/collect2.c
>>>>+++ b/gcc/collect2.c
>>>>@@ -859,18 +859,12 @@ main (int argc, char **argv)
>>>> {
>>>> USE_DEFAULT_LD,
>>>> USE_PLUGIN_LD,
>>>>- USE_GOLD_LD,
>>>>- USE_BFD_LD,
>>>>- USE_LLD_LD,
>>>>- USE_LD_MAX
>>>>+ USE_LD
>>>> } selected_linker = USE_DEFAULT_LD;
>>>>- static const char *const ld_suffixes[USE_LD_MAX] =
>>>>+ static const char *const ld_suffixes[USE_LD] =
>>>> {
>>>> "ld",
>>>>- PLUGIN_LD_SUFFIX,
>>>>- "ld.gold",
>>>>- "ld.bfd",
>>>>- "ld.lld"
>>>>+ PLUGIN_LD_SUFFIX
>>>> };
>>>> static const char *const real_ld_suffix = "real-ld";
>>>> static const char *const collect_ld_suffix = "collect-ld";
>>>>@@ -882,7 +876,7 @@ main (int argc, char **argv)
>>>> static const char *const strip_suffix = "strip";
>>>> static const char *const gstrip_suffix = "gstrip";
>>>>- const char *full_ld_suffixes[USE_LD_MAX];
>>>>+ const char *full_ld_suffixes[USE_LD];
>>>> #ifdef CROSS_DIRECTORY_STRUCTURE
>>>> /* If we look for a program in the compiler directories, we just use
>>>> the short name, since these directories are already system-specific.
>>>>@@ -924,6 +918,7 @@ main (int argc, char **argv)
>>>> const char **ld1;
>>>> bool use_plugin = false;
>>>> bool use_collect_ld = false;
>>>>+ const char *use_ld = NULL;
>>>> /* The kinds of symbols we will have to consider when scanning the
>>>> outcome of a first pass link. This is ALL to start with, then might
>>>>@@ -948,7 +943,7 @@ main (int argc, char **argv)
>>>> #endif
>>>> int i;
>>>>- for (i = 0; i < USE_LD_MAX; i++)
>>>>+ for (i = 0; i < USE_LD; i++)
>>>> full_ld_suffixes[i]
>>>> #ifdef CROSS_DIRECTORY_STRUCTURE
>>>> = concat (target_machine, "-", ld_suffixes[i], NULL);
>>>>@@ -1041,12 +1036,11 @@ main (int argc, char **argv)
>>>> if (selected_linker == USE_DEFAULT_LD)
>>>> selected_linker = USE_PLUGIN_LD;
>>>> }
>>>>- else if (strcmp (argv[i], "-fuse-ld=bfd") == 0)
>>>>- selected_linker = USE_BFD_LD;
>>>>- else if (strcmp (argv[i], "-fuse-ld=gold") == 0)
>>>>- selected_linker = USE_GOLD_LD;
>>>>- else if (strcmp (argv[i], "-fuse-ld=lld") == 0)
>>>>- selected_linker = USE_LLD_LD;
>>>>+ else if (!strncmp (argv[i], "-fuse-ld=", 9))
>>>>+ {
>>>>+ use_ld = argv[i] + 9;
>>>>+ selected_linker = USE_LD;
>>>>+ }
>>>> else if (strncmp (argv[i], "-o", 2) == 0)
>>>> {
>>>> /* Parse the output filename if it's given so that we can make
>>>>@@ -1152,8 +1146,7 @@ main (int argc, char **argv)
>>>> /* Maybe we know the right file to use (if not cross). */
>>>> ld_file_name = 0;
>>>> #ifdef DEFAULT_LINKER
>>>>- if (selected_linker == USE_BFD_LD || selected_linker == USE_GOLD_LD ||
>>>>- selected_linker == USE_LLD_LD)
>>>>+ if (!ld_file_name && selected_linker == USE_LD)
>>>> {
>>>> char *linker_name;
>>>> # ifdef HOST_EXECUTABLE_SUFFIX
>>>>@@ -1168,15 +1161,13 @@ main (int argc, char **argv)
>>>> if (! strcmp (&default_linker[len], HOST_EXECUTABLE_SUFFIX))
>>>> {
>>>> default_linker[len] = '\0';
>>>>- linker_name = concat (default_linker,
>>>>- &ld_suffixes[selected_linker][2],
>>>>+ linker_name = concat (default_linker, ".", use_ld,
>>>> HOST_EXECUTABLE_SUFFIX, NULL);
>>>> }
>>>> }
This piece of code (added by commit b78e932d513b7d3373bc5e1aab456dda737d07d0 PR driver/59321) is a bit complex.
The new patch does not touch it.
>>>> if (linker_name == NULL)
>>>> # endif
>>>>- linker_name = concat (DEFAULT_LINKER,
>>>>- &ld_suffixes[selected_linker][2],
>>>>+ linker_name = concat (DEFAULT_LINKER, ".", use_ld,
>>>> NULL);
>>>> if (access (linker_name, X_OK) == 0)
>>>> ld_file_name = linker_name;
>>>>@@ -1197,14 +1188,28 @@ main (int argc, char **argv)
>>>> ld_file_name = find_a_file (&cpath, collect_ld_suffix, X_OK);
>>>> use_collect_ld = ld_file_name != 0;
>>>> }
>>>>- /* Search the compiler directories for `ld'. We have protection against
>>>>- recursive calls in find_a_file. */
>>>>- if (ld_file_name == 0)
>>>>- ld_file_name = find_a_file (&cpath, ld_suffixes[selected_linker], X_OK);
>>>>- /* Search the ordinary system bin directories
>>>>- for `ld' (if native linking) or `TARGET-ld' (if cross). */
>>>>- if (ld_file_name == 0)
>>>>- ld_file_name = find_a_file (&path, full_ld_suffixes[selected_linker], X_OK);
>>>>+ if (selected_linker != USE_LD) {
>>>>+ /* Search the compiler directories for `ld'. We have protection against
>>>>+ recursive calls in find_a_file. */
>>>>+ if (!ld_file_name)
>>>>+ ld_file_name = find_a_file(&cpath, ld_suffixes[selected_linker], X_OK);
>>>>+ /* Search the ordinary system bin directories
>>>>+ for `ld' (if native linking) or `TARGET-ld' (if cross). */
>>>>+ if (!ld_file_name)
>>>>+ ld_file_name = find_a_file(&path, full_ld_suffixes[selected_linker], X_OK);
>>>>+ } else if (IS_ABSOLUTE_PATH(use_ld) && access(use_ld, X_OK) == 0) {
>>>>+ ld_file_name = use_ld;
>>>>+ } else {
>>>>+ const char *linker_name = concat("ld.", use_ld, NULL);
>>>
>>>This leads to strange searches like:
>>>
>>>$ strace -f -s512 gcc -fuse-ld=/x/y/z/pes /tmp/foo.c 2>&1 | grep pes
>>>...
>>>[pid 24295] stat("/home/marxin/bin/ld./x/y/z/pes", 0x7fffffffd1f0) = -1 ENOENT (No such file or directory)
>>>[pid 24295] stat("/usr/local/bin/ld./x/y/z/pes", 0x7fffffffd1f0) = -1 ENOENT (No such file or directory)
>>>
>>>Moreover, before the patch we only searched for suffixes 'ld.bfd', 'ld.gold' and 'ld.gold'. Now it
>>>searches also for:
>>>
>>>$ strace ... gcc -fuse-ld=xyz
>>>...
>>>[pid 24893] stat("/home/marxin/bin/ld.xyz", 0x7fffffffd200) = -1 ENOENT (No such file or directory)
>>>
>>>>+ if (!ld_file_name)
>>>>+ ld_file_name = find_a_file(&cpath, linker_name, X_OK);
>>>>+ if (!ld_file_name) {
>>>>+#ifdef CROSS_DIRECTORY_STRUCTURE
>>>>+ linker_name = concat(target_machine, "-", linker_name, NULL);
>>>>+#endif
>>>>+ ld_file_name = find_a_file(&path, linker_name, X_OK);
>>>>+ }
>>>>+ }
>>>> #ifdef REAL_NM_FILE_NAME
>>>> nm_file_name = find_a_file (&path, REAL_NM_FILE_NAME, X_OK);
>>>>diff --git a/gcc/common.opt b/gcc/common.opt
>>>>index 5692cd04374..a76ed6434bb 100644
>>>>--- a/gcc/common.opt
>>>>+++ b/gcc/common.opt
>>>>@@ -2859,17 +2859,9 @@ funwind-tables
>>>> Common Report Var(flag_unwind_tables) Optimization
>>>> Just generate unwind tables for exception handling.
>>>>-fuse-ld=bfd
>>>>-Common Driver Negative(fuse-ld=gold)
>>>>-Use the bfd linker instead of the default linker.
>>>>-
>>>>-fuse-ld=gold
>>>>-Common Driver Negative(fuse-ld=bfd)
>>>>-Use the gold linker instead of the default linker.
>>>>-
>>>>-fuse-ld=lld
>>>>-Common Driver Negative(fuse-ld=lld)
>>>>-Use the lld LLVM linker instead of the default linker.
>>>>+fuse-ld=
>>>>+Common Driver Joined
>>>>+-fuse-ld=[bfd|gold|lld|<absolute path>] Use the specified linker.
>>>> fuse-linker-plugin
>>>> Common Undocumented Var(flag_use_linker_plugin)
>>>>diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>>>index 35b341e759f..c2dd410c88f 100644
>>>>--- a/gcc/doc/invoke.texi
>>>>+++ b/gcc/doc/invoke.texi
>>>>@@ -14128,17 +14128,10 @@ uses @samp{nolto-rel}. To maintain whole program optimization, it is
>>>> recommended to link such objects into static library instead. Alternatively it
>>>> is possible to use H.J. Lu's binutils with support for mixed objects.
>>>>-@item -fuse-ld=bfd
>>>>-@opindex fuse-ld=bfd
>>>>-Use the @command{bfd} linker instead of the default linker.
>>>>-
>>>>-@item -fuse-ld=gold
>>>>-@opindex fuse-ld=gold
>>>>-Use the @command{gold} linker instead of the default linker.
>>>>-
>>>>-@item -fuse-ld=lld
>>>>-@opindex fuse-ld=lld
>>>>-Use the LLVM @command{lld} linker instead of the default linker.
>>>>+@item -fuse-ld=@var{linker}
>>>>+@opindex fuse-ld=linker
>>>>+If @var{linker} is an absolute path, use it instead of the default linker;
>>>>+otherwise use @command{ld.@var{linker}}.
>>>
>>>You should somehow mention the special values bfd,gold and ldd.
>>>> @cindex Libraries
>>>> @item -l@var{library}
>>>>diff --git a/gcc/gcc.c b/gcc/gcc.c
>>>>index effc384f3ef..f9a6f10502d 100644
>>>>--- a/gcc/gcc.c
>>>>+++ b/gcc/gcc.c
>>>>@@ -3989,12 +3989,8 @@ driver_handle_option (struct gcc_options *opts,
>>>> do_save = false;
>>>> break;
>>>>- case OPT_fuse_ld_bfd:
>>>>- use_ld = ".bfd";
>>>>- break;
>>>>-
>>>>- case OPT_fuse_ld_gold:
>>>>- use_ld = ".gold";
>>>>+ case OPT_fuse_ld_:
>>>>+ use_ld = arg;
>>>> break;
>>>> case OPT_fcompare_debug_second:
>>>>@@ -7903,20 +7899,20 @@ driver::maybe_print_and_exit () const
>>>> if (! strcmp (&default_linker[len], HOST_EXECUTABLE_SUFFIX))
>>>> {
>>>> default_linker[len] = '\0';
>>>>- ld = concat (default_linker, use_ld,
>>>>+ ld = concat (default_linker, ".", use_ld,
>>>> HOST_EXECUTABLE_SUFFIX, NULL);
>>>> }
>>>> }
>>>> if (ld == NULL)
>>>> # endif
>>>>- ld = concat (DEFAULT_LINKER, use_ld, NULL);
>>>>+ ld = concat (DEFAULT_LINKER, ".", use_ld, NULL);
>>>> if (access (ld, X_OK) == 0)
>>>> {
>>>> printf ("%s\n", ld);
>>>> return (0);
>>>> }
>>>> #endif
>>>>- print_prog_name = concat (print_prog_name, use_ld, NULL);
>>>>+ print_prog_name = concat (print_prog_name, ".", use_ld, NULL);
>>>
>>>In gcc.c you will probably have similar issues.
>>>
>>>> }
>>>> char *newname = find_a_file (&exec_prefixes, print_prog_name, X_OK, 0);
>>>> printf ("%s\n", (newname ? newname : print_prog_name));
>>>>diff --git a/gcc/opts.c b/gcc/opts.c
>>>>index 7affeb41a96..f50d365d517 100644
>>>>--- a/gcc/opts.c
>>>>+++ b/gcc/opts.c
>>>>@@ -2763,9 +2763,7 @@ common_handle_option (struct gcc_options *opts,
>>>> dc->max_errors = value;
>>>> break;
>>>>- case OPT_fuse_ld_bfd:
>>>>- case OPT_fuse_ld_gold:
>>>>- case OPT_fuse_ld_lld:
>>>>+ case OPT_fuse_ld_:
>>>> case OPT_fuse_linker_plugin:
>>>> /* No-op. Used by the driver and passed to us because it starts with f.*/
>>>> break;
>>>>
>>>
>
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