dtrace(1): add -d flag to dump D script post-dt_sugar

By specifying the -d flag, libdtrace will dump the D script after it has
applied syntactical sugar transformations (e.g if/else). This is useful
for both understanding what dt_sugar does, as well as debugging it.

Reviewed by:	markj
Approved by:	markj (mentor)
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D38732

4 files changed, 28 insertions, 10 deletions

diff --git a/cddl/contrib/opensolaris/cmd/dtrace/dtrace.1 b/cddl/contrib/opensolaris/cmd/dtrace/dtrace.1
index 8724b27f4cbb..c3c7b4cdc818 100644
--- a/cddl/contrib/opensolaris/cmd/dtrace/dtrace.1
+++ b/cddl/contrib/opensolaris/cmd/dtrace/dtrace.1
@@ -20,7 +20,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd September 7, 2021
+.Dd February 24, 2023
 .Dt DTRACE 1
 .Os
 .Sh NAME
@@ -29,7 +29,7 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl 32 | Fl 64
-.Op Fl aACeFGhHlqSvVwZ
+.Op Fl aACdeFGhHlqSvVwZ
 .Op Fl b Ar bufsz
 .Op Fl c Ar cmd
 .Op Fl D Ar name Op Ns = Ns value
@@ -195,6 +195,12 @@ option.
 For a description of the set of tokens defined by the D compiler when invoking
 the C preprocessor, see
 .Fl X .
+.It Fl d
+Dump the D script to standard output, after syntactic transformations have been
+applied.
+For example, if-statements in D are implemented using such transformations: a
+conditional clause in a probe body is replaced at compile-time by a separate
+probe predicated on the original condition.
 .It Fl D Ar name Op Ns = Ns value
 Define
 .Ar name
diff --git a/cddl/contrib/opensolaris/cmd/dtrace/dtrace.c b/cddl/contrib/opensolaris/cmd/dtrace/dtrace.c
index 06eff2055c17..cdc476a43b08 100644
--- a/cddl/contrib/opensolaris/cmd/dtrace/dtrace.c
+++ b/cddl/contrib/opensolaris/cmd/dtrace/dtrace.c
@@ -77,7 +77,7 @@ typedef struct dtrace_cmd {
 #define	E_USAGE		2
 
 static const char DTRACE_OPTSTR[] =
-	"3:6:aAb:Bc:CD:ef:FGhHi:I:lL:m:n:o:p:P:qs:SU:vVwx:X:Z";
+	"3:6:aAb:Bc:CdD:ef:FGhHi:I:lL:m:n:o:p:P:qs:SU:vVwx:X:Z";
 
 static char **g_argv;
 static int g_argc;
@@ -130,7 +130,7 @@ usage(FILE *fp)
 {
 	static const char predact[] = "[[ predicate ] action ]";
 
-	(void) fprintf(fp, "Usage: %s [-32|-64] [-aACeFGhHlqSvVwZ] "
+	(void) fprintf(fp, "Usage: %s [-32|-64] [-aACdeFGhHlqSvVwZ] "
 	    "[-b bufsz] [-c cmd] [-D name[=def]]\n\t[-I path] [-L path] "
 	    "[-o output] [-p pid] [-s script] [-U name]\n\t"
 	    "[-x opt[=val]] [-X a|c|s|t]\n\n"
@@ -152,6 +152,7 @@ usage(FILE *fp)
 	    "\t-b  set trace buffer size\n"
 	    "\t-c  run specified command and exit upon its completion\n"
 	    "\t-C  run cpp(1) preprocessor on script files\n"
+	    "\t-d  dump script after syntactic transformations\n"
 	    "\t-D  define symbol when invoking preprocessor\n"
 	    "\t-e  exit after compiling request but prior to enabling probes\n"
 	    "\t-f  enable or list probes matching the specified function name\n"
@@ -1559,6 +1560,10 @@ main(int argc, char *argv[])
 				g_cflags |= DTRACE_C_CPP;
 				break;
 
+			case 'd':
+				g_cflags |= DTRACE_C_SUGAR;
+				break;
+
 			case 'D':
 				if (dtrace_setopt(g_dtp, "define", optarg) != 0)
 					dfatal("failed to set -D %s", optarg);
diff --git a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_cc.c b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_cc.c
index e63771c91e08..f3fda4af834e 100644
--- a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_cc.c
+++ b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_cc.c
@@ -2478,10 +2478,7 @@ dt_compile(dtrace_hdl_t *dtp, int context, dtrace_probespec_t pspec, void *arg,
 		    "not referenced)\n", yypcb->pcb_sargv[argc - 1], argc - 1);
 	}
 
-	/*
-	 * Perform sugar transformations (for "if" / "else") and replace the
-	 * existing clause chain with the new one.
-	 */
+	/* Perform sugar transformations. */
 	if (context == DT_CTX_DPROG) {
 		dt_node_t *dnp, *next_dnp;
 		dt_node_t *new_list = NULL;
@@ -2492,8 +2489,17 @@ dt_compile(dtrace_hdl_t *dtp, int context, dtrace_probespec_t pspec, void *arg,
 			next_dnp = dnp->dn_list;
 			dnp->dn_list = NULL;
 
-			if (dnp->dn_kind == DT_NODE_CLAUSE)
+			if (dnp->dn_kind == DT_NODE_CLAUSE) {
 				dnp = dt_compile_sugar(dtp, dnp);
+				if (cflags & DTRACE_C_SUGAR) {
+					dt_node_t *p;
+
+					dt_printd(dnp, stdout, 0);
+					for (p = dnp->dn_list; p != NULL;
+					    p = p->dn_list)
+						dt_printd(p, stdout, 0);
+				}
+			}
 			/* append node to the new list */
 			new_list = dt_node_link(new_list, dnp);
 		}
diff --git a/cddl/contrib/opensolaris/lib/libdtrace/common/dtrace.h b/cddl/contrib/opensolaris/lib/libdtrace/common/dtrace.h
index f0bc83a7fc7b..af0213695f32 100644
--- a/cddl/contrib/opensolaris/lib/libdtrace/common/dtrace.h
+++ b/cddl/contrib/opensolaris/lib/libdtrace/common/dtrace.h
@@ -119,10 +119,11 @@ typedef struct dtrace_proginfo {
 #define	DTRACE_C_PSPEC	0x0080	/* Interpret ambiguous specifiers as probes */
 #define	DTRACE_C_ETAGS	0x0100	/* Prefix error messages with error tags */
 #define	DTRACE_C_ARGREF	0x0200	/* Do not require all macro args to be used */
+#define	DTRACE_C_SUGAR	0x0400	/* Dump D script post-dt_sugar */
 #define	DTRACE_C_DEFARG	0x0800	/* Use 0/"" as value for unspecified args */
 #define	DTRACE_C_NOLIBS	0x1000	/* Do not process D system libraries */
 #define	DTRACE_C_CTL	0x2000	/* Only process control directives */
-#define	DTRACE_C_MASK	0x3bff	/* mask of all valid flags to dtrace_*compile */
+#define	DTRACE_C_MASK	0x3fff	/* mask of all valid flags to dtrace_*compile */
 
 extern dtrace_prog_t *dtrace_program_strcompile(dtrace_hdl_t *,
     const char *, dtrace_probespec_t, uint_t, int, char *const []);