Re: [PATCH] mksigtab.sh: Add support for musl libc

Re: [PATCH] mksigtab.sh: Add support for musl libc

[Ian Lance Taylor]

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On Fri, Apr 15, 2022 at 6:38 AM Sören Tempel <soeren@soeren-tempel.net> wrote:
>
> Attached are two small git-format-patch(1) files which add support for
> musl libc to gofrontend's mksigtab.sh script. They address the following
> issues:
>
>         * Signal 34 is special on musl and is used internally for
>           setgid <https://github.com/golang/go/issues/39343>.
>         * SIGPOLL uses the same signal number as SIGIO on musl. This
>           causes a build failure as the map keys are not unique then.
>
> Let me know if you need me to provide more information or if the patches
> need to be revised in any way.

Thanks, both committed.

Going forward please use the process at
https://go.dev/doc/gccgo_contribute or also send the patches to
gcc-patches@gcc.gnu.org.  Thanks.

Ian

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208b7d85d73cbd166e207f0e062cccbdfbf52bb3
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index bcb526c85b9..eeff61d82f8 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-62fc90f52da2f52cbe3b4f10e560dc6aa59baeb5
+8336fe4a5da68d9188dfbc4fb647ccbbe4d60ba4
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/libgo/go/runtime/signal_gccgo.go b/libgo/go/runtime/signal_gccgo.go
index 2eece687e35..82e6996ab7e 100644
--- a/libgo/go/runtime/signal_gccgo.go
+++ b/libgo/go/runtime/signal_gccgo.go
@@ -106,7 +106,8 @@ func getsig(i uint32) uintptr {
 	if sigaction(i, nil, &sa) < 0 {
 		// On GNU/Linux glibc rejects attempts to call
 		// sigaction with signal 32 (SIGCANCEL) or 33 (SIGSETXID).
-		if GOOS == "linux" && (i == 32 || i == 33) {
+		// On musl signal 34 (SIGSYNCCALL) also needs to be treated accordingly.
+		if GOOS == "linux" && (i == 32 || i == 33 || i == 34) {
 			return _SIG_DFL
 		}
 		throw("sigaction read failure")
diff --git a/libgo/mksigtab.sh b/libgo/mksigtab.sh
index 11e4ec436bd..cdf6fcd823f 100644
--- a/libgo/mksigtab.sh
+++ b/libgo/mksigtab.sh
@@ -95,10 +95,12 @@ checksig _SIGLOST '   {_SigNotify, "SIGLOST: resource lost (Sun); server died (G
 
 # Special handling of signals 32 and 33 on GNU/Linux systems,
 # because they are special to glibc.
+# Signal 34 is additionally special to Linux systems with musl.
 if test "${GOOS}" = "linux"; then
-    SIGLIST=$SIGLIST"_32__33_"
+    SIGLIST=$SIGLIST"_32__33__34_"
     echo '	32: {_SigSetStack + _SigUnblock, "signal 32"}, /* SIGCANCEL; see issue 6997 */'
     echo '	33: {_SigSetStack + _SigUnblock, "signal 33"}, /* SIGSETXID; see issues 3871, 9400, 12498 */'
+    echo '	34: {_SigSetStack + _SigUnblock, "signal 34"}, /* musl SIGSYNCCALL; see issue 39343 */'
 fi
 
 if test "${GOOS}" = "aix"; then

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ace4928a29b79ac6aa0c84d6fd78f5dce5fa6190
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index eeff61d82f8..2321f67ca5d 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-8336fe4a5da68d9188dfbc4fb647ccbbe4d60ba4
+22b0ccda3aa4d16f770a26a3eb251f8da615c318
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
diff --git a/libgo/mksigtab.sh b/libgo/mksigtab.sh
index cdf6fcd823f..bea8739957e 100644
--- a/libgo/mksigtab.sh
+++ b/libgo/mksigtab.sh
@@ -26,7 +26,6 @@ SIGLIST=""
 # Handle signals valid on all Unix systems.
 
 addsig() {
-    echo "	$1: $2,"
     # Get the signal number and add it to SIGLIST
     signum=`grep "const $1 = " gen-sysinfo.go | sed -e 's/.* = //'`
     if echo "$signum" | grep '^_SIG[A-Z0-9_]*$' >/dev/null 2>&1; then
@@ -34,7 +33,12 @@ addsig() {
         # This is needed for some MIPS signals defined as aliases of other signals
         signum=`grep "const $signum = " gen-sysinfo.go | sed -e 's/.* = //'`
     fi
-    SIGLIST=$SIGLIST"_${signum}_"
+    # Only add signal if the signal number isn't in the list yet.
+    # For example, musl libc uses signal 29 for both SIGIO and SIGPOLL.
+    if ! echo "$SIGLIST" | grep "_${signum}_" >/dev/null 2>&1; then
+        echo "	$1: $2,"
+        SIGLIST=$SIGLIST"_${signum}_"
+    fi
 }
 
 echo '	0:          {0, "SIGNONE: no trap"},'