[DTrace-devel] [PATCH 2/2] Use asprintf() to allocate strings

[eugene.loh at oracle.com]

From: Eugene Loh <eugene.loh at oracle.com>

Earlier patches have slowly replaced constructs like:
    int len;
    len = snprintf(NULL, 0, format, args) + 1;
    buf = malloc(len);
    snprintf(buf, len, format, args);
with the more compact:
    asprintf(&buf, format, args);

Replace the remaining instances of the bulkier construct.

Note that dt_conf_init() continues to compute a buffer length and
allocate a buffer, since that buffer will be reused multiple times.

Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
---
 libdtrace/dt_link.c        | 17 +++++++----------
 libdtrace/dt_probe.c       | 11 +++--------
 libdtrace/dt_prov_dtrace.c | 12 +++---------
 3 files changed, 13 insertions(+), 27 deletions(-)

diff --git a/libdtrace/dt_link.c b/libdtrace/dt_link.c
index c9e0ea5fe..ffa16d9a4 100644
--- a/libdtrace/dt_link.c
+++ b/libdtrace/dt_link.c
@@ -1,6 +1,6 @@
 /*
  * Oracle Linux DTrace.
- * Copyright (c) 2008, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2026, Oracle and/or its affiliates. All rights reserved.
  * Licensed under the Universal Permissive License v 1.0 as shown at
  * http://oss.oracle.com/licenses/upl.
  */
@@ -416,7 +416,6 @@ dtrace_program_link(dtrace_hdl_t *dtp, dtrace_prog_t *pgp, uint_t dflags,
 	char drti[PATH_MAX], symvers[PATH_MAX];
 	int fd, i, cur;
 	char *cmd;
-	size_t len;
 	int ret = 0, status = 0;
 
 	/*
@@ -426,6 +425,7 @@ dtrace_program_link(dtrace_hdl_t *dtp, dtrace_prog_t *pgp, uint_t dflags,
 	 */
 	if (pgp == NULL) {
 		const char *fmt = "%s -o %s -r";
+		size_t len;
 
 		len = snprintf(NULL, 0, fmt, dtp->dt_ld_path, file) + 1;
 
@@ -521,15 +521,12 @@ dtrace_program_link(dtrace_hdl_t *dtp, dtrace_prog_t *pgp, uint_t dflags,
 		}
 		snprintf(symvers, sizeof (symvers), "%s/drti/drti-vers", libdir->dir_path);
 
-		len = snprintf(NULL, 0, fmt, dtp->dt_ld_path, emu, file,
-			       symvers, fd, drti) + 1;
+		asprintf(&cmd, fmt, dtp->dt_ld_path, emu, file, symvers, fd,
+			 drti);
+		status = system(cmd);
+		free(cmd);
 
-		cmd = alloca(len);
-
-		(void) snprintf(cmd, len, fmt, dtp->dt_ld_path, emu, file,
-				symvers, fd, drti);
-
-		if ((status = system(cmd)) == -1) {
+		if (status == -1) {
 			ret = dt_link_error(dtp, NULL, -1,
 			    "failed to run %s: %s", dtp->dt_ld_path,
 			    strerror(errno));
diff --git a/libdtrace/dt_probe.c b/libdtrace/dt_probe.c
index 65316f515..86353893f 100644
--- a/libdtrace/dt_probe.c
+++ b/libdtrace/dt_probe.c
@@ -1,6 +1,6 @@
 /*
  * Oracle Linux DTrace.
- * Copyright (c) 2006, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2006, 2026, Oracle and/or its affiliates. All rights reserved.
  * Licensed under the Universal Permissive License v 1.0 as shown at
  * http://oss.oracle.com/licenses/upl.
  */
@@ -475,15 +475,9 @@ dt_probe_tag(dt_probe_t *prp, uint_t argn, dt_node_t *dnp)
 {
 	dtrace_hdl_t *dtp = prp->prov->pv_hdl;
 	dtrace_typeinfo_t dtt;
-	size_t len;
 	char *tag;
 
-	len = snprintf(NULL, 0, "__dtrace_%s___%s_arg%u",
-	    prp->prov->desc.dtvd_name, prp->pr_name, argn);
-
-	tag = alloca(len + 1);
-
-	snprintf(tag, len + 1, "__dtrace_%s___%s_arg%u",
+	asprintf(&tag, "__dtrace_%s___%s_arg%u",
 	    prp->prov->desc.dtvd_name, prp->pr_name, argn);
 
 	if (dtrace_lookup_by_type(dtp, DTRACE_OBJ_DDEFS, tag, &dtt) != 0) {
@@ -498,6 +492,7 @@ dt_probe_tag(dt_probe_t *prp, uint_t argn, dt_node_t *dnp)
 			    tag, ctf_errmsg(ctf_errno(dtt.dtt_ctfp)));
 		}
 	}
+	free(tag);
 
 	memset(dnp, 0, sizeof(dt_node_t));
 	dnp->dn_kind = DT_NODE_TYPE;
diff --git a/libdtrace/dt_prov_dtrace.c b/libdtrace/dt_prov_dtrace.c
index 102afd84e..d417a864b 100644
--- a/libdtrace/dt_prov_dtrace.c
+++ b/libdtrace/dt_prov_dtrace.c
@@ -232,7 +232,6 @@ static int attach(dtrace_hdl_t *dtp, const dt_probe_t *prp, int bpf_fd)
 		char	*spec;
 		char	*fn;
 		FILE	*f;
-		size_t	len;
 		int	fd, rc = -1;
 
 		/* get a uprobe specification for this probe */
@@ -252,16 +251,11 @@ static int attach(dtrace_hdl_t *dtp, const dt_probe_t *prp, int bpf_fd)
 			return -ENOENT;
 
 		/* open format file */
-		len = snprintf(NULL, 0, "%s" PROBE_FMT "/format",
-			       EVENTSFS, PROBE_DATA) + 1;
-		fn = dt_alloc(dtp, len);
-		if (fn == NULL)
+		if (asprintf(&fn, "%s" PROBE_FMT "/format", EVENTSFS,
+			     PROBE_DATA) < 0)
 			return -ENOENT;
-
-		snprintf(fn, len, "%s" PROBE_FMT "/format",
-			 EVENTSFS, PROBE_DATA);
 		f = fopen(fn, "r");
-		dt_free(dtp, fn);
+		free(fn);
 		if (f == NULL)
 			return -ENOENT;
 
-- 
2.47.3