diff --git a/app-shells/smrsh/files/site.config.m4 b/app-shells/smrsh/files/site.config.m4
index 24ef462ba2eb8..1b7b0db958215 100644
--- a/app-shells/smrsh/files/site.config.m4
+++ b/app-shells/smrsh/files/site.config.m4
@@ -1,6 +1,6 @@
 define(`confCCOPTS', `@@confCCOPTS@@')
 define(`confSTDIO_TYPE', `portable')
-define(`confENVDEF', `-DXDEBUG=0')
+define(`confENVDEF', `@@confENVDEF@@')
 define(`confLDOPTS', `@@confLDOPTS@@')
 define(`confMANOWN', `root')
 define(`confMANGRP', `root')
diff --git a/app-shells/smrsh/files/smrsh-8.18.1-c23-sm_strtoll.patch b/app-shells/smrsh/files/smrsh-8.18.1-c23-sm_strtoll.patch
new file mode 100644
index 0000000000000..63d64b0164cec
--- /dev/null
+++ b/app-shells/smrsh/files/smrsh-8.18.1-c23-sm_strtoll.patch
@@ -0,0 +1,29 @@
+Bug: https://bugs.gentoo.org/944460
+
+--- a/libsm/vfscanf.c
++++ b/libsm/vfscanf.c
+@@ -240,13 +240,13 @@
+ 			/* FALLTHROUGH */
+ 		  case 'd':
+ 			c = CT_INT;
+-			ccfn = (ULONGLONG_T (*)())sm_strtoll;
++			ccfn = (ULONGLONG_T (*)(const char *, char **, int))sm_strtoll;
+ 			base = 10;
+ 			break;
+ 
+ 		  case 'i':
+ 			c = CT_INT;
+-			ccfn = (ULONGLONG_T (*)())sm_strtoll;
++			ccfn = (ULONGLONG_T (*)(const char *, char **, int))sm_strtoll;
+ 			base = 0;
+ 			break;
+ 
+@@ -324,7 +324,7 @@
+ 			if (isupper(c))
+ 				flags |= LONG;
+ 			c = CT_INT;
+-			ccfn = (ULONGLONG_T (*)()) sm_strtoll;
++			ccfn = (ULONGLONG_T (*)(const char *, char **, int)) sm_strtoll;
+ 			base = 10;
+ 			break;
+ 		}
diff --git a/app-shells/smrsh/files/smrsh-musl-disable-cdefs.patch b/app-shells/smrsh/files/smrsh-musl-disable-cdefs.patch
new file mode 100644
index 0000000000000..6dc4ac63105e2
--- /dev/null
+++ b/app-shells/smrsh/files/smrsh-musl-disable-cdefs.patch
@@ -0,0 +1,11 @@
+--- a/include/sm/os/sm_os_linux.h	2020-06-09 11:57:46.789786561 +0200
++++ b/include/sm/os/sm_os_linux.h	2020-06-09 11:57:49.174781812 +0200
+@@ -33,7 +33,7 @@
+ # endif /* LINUX_VERSION_CODE */
+ #endif /* SM_CONF_SHM */
+
+-#define SM_CONF_SYS_CDEFS_H	1
++#define SM_CONF_SYS_CDEFS_H	0
+ #ifndef SM_CONF_SEM
+ # define SM_CONF_SEM	2
+ #endif /* SM_CONF_SEM */
diff --git a/app-shells/smrsh/smrsh-8.15.2-r1.ebuild b/app-shells/smrsh/smrsh-8.15.2-r1.ebuild
index bada1d80ba8b3..e634c33f2ab71 100644
--- a/app-shells/smrsh/smrsh-8.15.2-r1.ebuild
+++ b/app-shells/smrsh/smrsh-8.15.2-r1.ebuild
@@ -26,6 +26,15 @@ DEPEND="${RDEPEND}
 	sys-devel/m4"
 
 src_prepare() {
+	local confENVDEF="-DXDEBUG=0"
+
+	eapply "${FILESDIR}"/${PN}-8.18.1-c23-sm_strtoll.patch
+
+	if use elibc_musl; then
+		eapply "${FILESDIR}"/${PN}-musl-disable-cdefs.patch
+		confENVDEF+=" -DHASSTRERROR"
+	fi
+
 	cd "${S}/${PN}" || die
 
 	default
@@ -36,6 +45,7 @@ src_prepare() {
 
 	sed -e "s|@@confCCOPTS@@|${CFLAGS}|" \
 		-e "s|@@confLDOPTS@@|${LDFLAGS}|" \
+		-e "s|@@confENVDEF@@|${confENVDEF}|" \
 		-e "s:@@confCC@@:$(tc-getCC):" "${FILESDIR}/site.config.m4" \
 		> "${S}/devtools/Site/site.config.m4" || die "sed failed"
 }
diff --git a/app-shells/smrsh/smrsh-8.18.1.ebuild b/app-shells/smrsh/smrsh-8.18.1.ebuild
index bada1d80ba8b3..e634c33f2ab71 100644
--- a/app-shells/smrsh/smrsh-8.18.1.ebuild
+++ b/app-shells/smrsh/smrsh-8.18.1.ebuild
@@ -26,6 +26,15 @@ DEPEND="${RDEPEND}
 	sys-devel/m4"
 
 src_prepare() {
+	local confENVDEF="-DXDEBUG=0"
+
+	eapply "${FILESDIR}"/${PN}-8.18.1-c23-sm_strtoll.patch
+
+	if use elibc_musl; then
+		eapply "${FILESDIR}"/${PN}-musl-disable-cdefs.patch
+		confENVDEF+=" -DHASSTRERROR"
+	fi
+
 	cd "${S}/${PN}" || die
 
 	default
@@ -36,6 +45,7 @@ src_prepare() {
 
 	sed -e "s|@@confCCOPTS@@|${CFLAGS}|" \
 		-e "s|@@confLDOPTS@@|${LDFLAGS}|" \
+		-e "s|@@confENVDEF@@|${confENVDEF}|" \
 		-e "s:@@confCC@@:$(tc-getCC):" "${FILESDIR}/site.config.m4" \
 		> "${S}/devtools/Site/site.config.m4" || die "sed failed"
 }