[binutils-gdb] gas: add a means to programmatically determine the assembler version
Jan Beulich
jbeulich@sourceware.org
Fri Jul 4 08:42:45 GMT 2025
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=7b40f4c6587c04794d08e805eb17c61c629ab662
commit 7b40f4c6587c04794d08e805eb17c61c629ab662
Author: Jan Beulich <jbeulich@suse.com>
Date: Fri Jul 4 10:41:34 2025 +0200
gas: add a means to programmatically determine the assembler version
It has been more than once that I would have wanted to have a way to
know the gas version in assembly sources, perhaps for use with .if. Add
such a pre-defined symbol, introducing the common pattern GAS(<symbol>)
for any such symbols. The use of parentheses is to keep the risk of
collisions with users' symbols as low as possible. (Possible future
arch-specific symbols may want to use GAS(<arch>:<symbol>).)
Similarly permit determining whether the assembler is a released
version. The exact value probably isn't of much use, it's more the
defined-ness that one might care about. Yet the symbol needs to have
some value anyway.
While by default pre-defined symbols won't be emitted to the symbol
table, introduce -emit-local-absolute to allow requesting this. Re-
purpose flag_strip_local_absolute to become tristate, with a negative
value indicating to also emit pre-defined symbols.
Diff:
---
gas/NEWS | 3 +++
gas/as.c | 30 ++++++++++++++++++++++++++++++
gas/as.h | 4 +++-
gas/doc/as.texi | 29 +++++++++++++++++++++++++++++
gas/symbols.c | 2 +-
gas/testsuite/gas/all/gas.exp | 27 +++++++++++++++++++++++++++
gas/testsuite/gas/all/version.d | 7 +++++++
gas/testsuite/gas/all/version.s | 4 ++++
gas/testsuite/gas/all/version2.d | 3 +++
gas/testsuite/gas/all/version3.d | 8 ++++++++
10 files changed, 115 insertions(+), 2 deletions(-)
diff --git a/gas/NEWS b/gas/NEWS
index f0ffe2db54b..e48cee30bac 100644
--- a/gas/NEWS
+++ b/gas/NEWS
@@ -1,5 +1,8 @@
-*- text -*-
+* Predefined symbols "GAS(version)" and, on non-release builds, "GAS(date)" are
+ now being made available.
+
* Support for x86 AVX10.2 256 bit rounding has been dropped, as all the
hardware would directly support 512 bit vecotr width.
diff --git a/gas/as.c b/gas/as.c
index a37d59d4649..c7de3a9f4e8 100644
--- a/gas/as.c
+++ b/gas/as.c
@@ -486,6 +486,7 @@ parse_args (int * pargc, char *** pargv)
OPTION_GDWARF_CIE_VERSION,
OPTION_GCODEVIEW,
OPTION_STRIP_LOCAL_ABSOLUTE,
+ OPTION_EMIT_LOCAL_ABSOLUTE,
OPTION_TRADITIONAL_FORMAT,
OPTION_WARN,
OPTION_TARGET_HELP,
@@ -590,6 +591,7 @@ parse_args (int * pargc, char *** pargv)
,{"reduce-memory-overheads", no_argument, NULL, OPTION_REDUCE_MEMORY_OVERHEADS}
,{"statistics", no_argument, NULL, OPTION_STATISTICS}
,{"strip-local-absolute", no_argument, NULL, OPTION_STRIP_LOCAL_ABSOLUTE}
+ ,{"emit-local-absolute", no_argument, NULL, OPTION_EMIT_LOCAL_ABSOLUTE}
,{"version", no_argument, NULL, OPTION_VERSION}
,{"verbose", no_argument, NULL, 'v'}
,{"target-help", no_argument, NULL, OPTION_TARGET_HELP}
@@ -688,6 +690,10 @@ parse_args (int * pargc, char *** pargv)
flag_strip_local_absolute = 1;
break;
+ case OPTION_EMIT_LOCAL_ABSOLUTE:
+ flag_strip_local_absolute = -1;
+ break;
+
case OPTION_TRADITIONAL_FORMAT:
flag_traditional_format = 1;
break;
@@ -1163,6 +1169,26 @@ This program has absolutely no warranty.\n"));
#endif
}
+/* Pre-define a symbol with its name derived from TMPL (wrapping in
+ GAS(...)), to value VAL. */
+
+void
+predefine_symbol (const char *tmpl, valueT val)
+{
+ char *name = xasprintf ("GAS(%s)", tmpl);
+ symbolS *s;
+
+ /* Also put the symbol in the symbol table, if requested. */
+ if (flag_strip_local_absolute < 0)
+ s = symbol_new (name, absolute_section, &zero_address_frag, val);
+ else
+ s = symbol_create (name, absolute_section, &zero_address_frag, val);
+ S_CLEAR_EXTERNAL (s);
+ symbol_table_insert (s);
+
+ xfree (name);
+}
+
static void
dump_statistics (void)
{
@@ -1205,6 +1231,10 @@ perform_an_assembly_pass (int argc, char ** argv)
subseg_set (text_section, 0);
#endif
+ predefine_symbol ("version", BFD_VERSION);
+ if (strstr (BFD_VERSION_STRING, "." XSTRING (BFD_VERSION_DATE)) != NULL)
+ predefine_symbol ("date", BFD_VERSION_DATE);
+
/* This may add symbol table entries, which requires having an open BFD,
and sections already created. */
md_begin ();
diff --git a/gas/as.h b/gas/as.h
index 4b5f78b53d0..872c6ddf393 100644
--- a/gas/as.h
+++ b/gas/as.h
@@ -339,7 +339,8 @@ COMMON enum synth_cfi_type flag_synth_cfi;
/* This is true if the assembler should output time and space usage. */
COMMON unsigned char flag_print_statistics;
-/* True if local absolute symbols are to be stripped. */
+/* True (positive) if local absolute symbols are to be stripped. Negative if
+ even pre-defined symbols should be emitted. */
COMMON int flag_strip_local_absolute;
/* True if we should generate a traditional format object file. */
@@ -514,6 +515,7 @@ void as_report_context (void);
const char * as_where (unsigned int *);
const char * as_where_top (unsigned int *);
const char * as_where_physical (unsigned int *);
+void predefine_symbol (const char *, valueT);
void bump_line_counters (void);
void do_scrub_begin (int);
void input_scrub_begin (void);
diff --git a/gas/doc/as.texi b/gas/doc/as.texi
index 7d6cdcb0a73..e17c2df40db 100644
--- a/gas/doc/as.texi
+++ b/gas/doc/as.texi
@@ -779,6 +779,10 @@ symbols with the @code{STT_COMMON} type. The default can be controlled
by a configure option @option{--enable-elf-stt-common}.
@end ifset
+@item --emit-local-absolute
+Emit even pre-defined (local) absolute symbols to the outgoing symbol table.
+Note that this isn't the exact opposite of @samp{--strip-local-absolute}.
+
@item --emulation=@var{name}
If the assembler is configured to support multiple different target
configurations then this option can be used to select the desired form.
@@ -3909,6 +3913,7 @@ the same order they were declared. This may break some debuggers.
* Symbol Names:: Symbol Names
* Dot:: The Special Dot Symbol
* Symbol Attributes:: Symbol Attributes
+* Predefined Symbols:: Predefined Symbols
@end menu
@node Labels
@@ -4250,6 +4255,30 @@ Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
@code{EXPORT} assembler directive documentation.
@end ifset
+@node Predefined Symbols
+@section Predefined Symbols
+
+Certain pre-defined symbols will be made available for use, and possibly also
+inserted in the symbol table. Because of the use of parentheses, access to
+these symbols will require quotation.
+
+Independent of the specific target, the following symbols will (perhaps
+conditionally; see each individual item) be made available:
+@itemize @bullet
+
+@item @code{GAS(version)}
+The version of the assembler, expressed as @samp{major} @code{*} 100000000
+@code{+} @samp{minor} @code{*} 1000000 @code{+} @samp{rev} @code{*} 10000.
+
+@item @code{GAS(date)}
+The date of the assembler sources (which may not be the date the assembler was
+built). This is added only for non-release versions of gas. The specific
+value probably better isn't checked for, just its defined-ness.
+
+@end itemize
+
+All symbols of the form @code{GAS(...)} are reserved for use by GNU @value{AS}.
+
@node Expressions
@chapter Expressions
diff --git a/gas/symbols.c b/gas/symbols.c
index 45b7d9b95e6..02ea741bde2 100644
--- a/gas/symbols.c
+++ b/gas/symbols.c
@@ -2428,7 +2428,7 @@ S_IS_LOCAL (const symbolS *s)
flags = s->bsym->flags;
- if (flag_strip_local_absolute
+ if (flag_strip_local_absolute > 0
/* Keep BSF_FILE symbols in order to allow debuggers to identify
the source file even when the object file is stripped. */
&& (flags & (BSF_GLOBAL | BSF_FILE)) == 0
diff --git a/gas/testsuite/gas/all/gas.exp b/gas/testsuite/gas/all/gas.exp
index 780838d246d..41d35285c7b 100644
--- a/gas/testsuite/gas/all/gas.exp
+++ b/gas/testsuite/gas/all/gas.exp
@@ -566,3 +566,30 @@ run_dump_test "multibyte1"
run_dump_test "multibyte2"
run_list_test "multibyte3" "--multibyte-handling=warn"
run_list_test "multibyte3" "-f --multibyte-handling=warn"
+
+# EVAX has an extra line printed by objdump when there are no relocations,
+# and doesn't appear to enter absolute symbols into the symbol table.
+# SOM (HPPA) won't properly handle at least the latter two tests.
+switch -glob $target_triplet {
+ alpha-*-*vms* { }
+ hppa-*-hpux* { }
+ default {
+ run_dump_test "version"
+ # Non-ELF symbol tables may include section symbols.
+ # MSP430 adds references to library symbols.
+ # RL78 includes a special absolute symbol.
+ if { [is_elf_format]
+ && ![istarget "msp430*-*-*"]
+ && ![istarget "rl78*-*-*"] } {
+ run_dump_test "version2"
+ }
+ # ECOFF/XCOFF don't look to (reliably) emit local absolute symbols.
+ # IA64, when targeting HPUX, deliberately omits unreferenced symbols.
+ if { ![is_xcoff_format]
+ && ![istarget "alpha-*-linux*ecoff*"]
+ && ![istarget "alpha-*-osf*"]
+ && ![istarget "ia64-*-hpux*"] } {
+ run_dump_test "version3"
+ }
+ }
+}
diff --git a/gas/testsuite/gas/all/version.d b/gas/testsuite/gas/all/version.d
new file mode 100644
index 00000000000..9803619b529
--- /dev/null
+++ b/gas/testsuite/gas/all/version.d
@@ -0,0 +1,7 @@
+#objdump: -rsj .data
+#name: pre-defined version symbol
+
+.*: +file format .*
+
+Contents of section .data:
+ 0+ [0-9a-f]*[1-9a-f][0-9a-f]* .*
diff --git a/gas/testsuite/gas/all/version.s b/gas/testsuite/gas/all/version.s
new file mode 100644
index 00000000000..3f3d8243186
--- /dev/null
+++ b/gas/testsuite/gas/all/version.s
@@ -0,0 +1,4 @@
+ .data
+ .ifdef "GAS(version)"
+ .dc.l "GAS(version)"
+ .endif
diff --git a/gas/testsuite/gas/all/version2.d b/gas/testsuite/gas/all/version2.d
new file mode 100644
index 00000000000..9b211c0ebb9
--- /dev/null
+++ b/gas/testsuite/gas/all/version2.d
@@ -0,0 +1,3 @@
+#nm: --quiet
+#name: pre-defined version symbol (empty symbol table)
+#source: version.s
diff --git a/gas/testsuite/gas/all/version3.d b/gas/testsuite/gas/all/version3.d
new file mode 100644
index 00000000000..aff9ad65702
--- /dev/null
+++ b/gas/testsuite/gas/all/version3.d
@@ -0,0 +1,8 @@
+#as: -emit-local-absolute
+#nm: -f bsd
+#name: pre-defined version symbol (non-empty symbol table)
+#source: version.s
+
+#...
+.* a GAS\(version\)
+#pass
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