47358: Add a ZSH_XTRACEFD environment variable to redirect debug traces

Src/exec.c

@@ -5543,7 +5543,7 @@ execshfunc(Shfunc shf, LinkList args)
     cmdsp = 0;
     if ((osfc = sfcontext) == SFC_NONE)
 	sfcontext = SFC_DIRECT;
-    xtrerr = stderr;
+    xtrerr = xtrace_file;
 
     doshfunc(shf, args, 0);
 

Src/init.c

@@ -619,8 +619,10 @@ init_io(char *cmd)
 	SHTTY = -1;
     }
 
-    /* Send xtrace output to stderr -- see execcmd() */
-    xtrerr = stderr;
+    /* Send xtrace output to zsh_xtracefd file descriptor -- see execcmd() */
+    if (zsh_xtracefd == 0)
+       zsh_xtracefd = 2;
+    xtracefdassign();
 
     /* Make sure the tty is opened read/write. */
     if (isatty(0)) {

Src/params.c

@@ -107,7 +107,8 @@ mod_export zlong
      zterm_lines,	/* $LINES       */
      rprompt_indent,	/* $ZLE_RPROMPT_INDENT */
      ppid,		/* $PPID        */
-     zsh_subshell;	/* $ZSH_SUBSHELL */
+     zsh_subshell,	/* $ZSH_SUBSHELL */
+     zsh_xtracefd;	/* $ZSH_XTRACEFD */
 
 /* $FUNCNEST    */
 /**/
@@ -270,6 +271,9 @@ static const struct gsu_array pipestatus_gsu =
 static const struct gsu_integer rprompt_indent_gsu =
 { intvargetfn, zlevarsetfn, rprompt_indent_unsetfn };
 
+static const struct gsu_integer xtracefd_gsu =
+{ intvargetfn, xtracefdsetfn, xtracefdunsetfn };
+
 /* Nodes for special parameters for parameter hash table */
 
 #ifdef HAVE_UNION_INIT
@@ -359,6 +363,7 @@ IPDEF5("LINES", &zterm_lines, zlevar_gsu),
 IPDEF5U("ZLE_RPROMPT_INDENT", &rprompt_indent, rprompt_indent_gsu),
 IPDEF5("SHLVL", &shlvl, varinteger_gsu),
 IPDEF5("FUNCNEST", &zsh_funcnest, varinteger_gsu),
+IPDEF5("ZSH_XTRACEFD", &zsh_xtracefd, xtracefd_gsu),
 
 /* Don't import internal integer status variables. */
 #define IPDEF6(A,B,F) {{NULL,A,PM_INTEGER|PM_SPECIAL|PM_DONTIMPORT},BR((void *)B),GSU(F),10,0,NULL,NULL,NULL,0}
@@ -4562,6 +4567,65 @@ setsecondstype(Param pm, int on, int off)
     return 0;
 }
 
+/* Open / assign the XTRACE fd */
+
+/**/
+void xtracefdassign(void)
+{
+    int fd = (int)zsh_xtracefd;
+    switch (fd)
+    {
+    case 0:                    /* bizarre, but handle for consistency */
+       xtrerr = stdin;
+       break;
+
+    case 1:
+       xtrerr = stdout;
+       break;
+
+    case 2:
+       xtrerr = stderr;
+       break;
+
+    default:
+       xtrerr = fdopen(fd, "w");
+       break;
+    }
+    xtrace_file = xtrerr;
+}
+
+/* Function to set value of special parameter `ZSH_XTRACEFD' */
+
+/**/
+void
+xtracefdsetfn(Param pm, zlong fd)
+{
+    /* Check that the given file descriptor is valid */
+    if (fcntl(fd, F_GETFD) != -1 || errno != EBADF) {
+      intvarsetfn(pm, fd);
+      xtracefdassign();
+    } else
+      zwarn("file descriptor %d is not valid", fd);
+
+}
+
+/* Function to unset value of special parameter `ZSH_XTRACEFD' */
+
+/**/
+void
+xtracefdunsetfn(Param pm, UNUSED(int exp))
+{
+    int current_fd = intvargetfn(pm);
+    if (current_fd == 2)  /* Nothing to do, already using stderr */
+      return;
+    else {  /* Reset to file descriptor 2 (stderr) */
+      intvarsetfn(pm, 2);
+    //   if (current_fd > 2)
+    //      fclose(xtrerr);  /* Never close standard descriptors */
+      xtrerr = xtrace_file = stderr;
+    }
+}
+
 /* Function to get value for special parameter `USERNAME' */
 
 /**/

Src/utils.c

@@ -1699,12 +1699,19 @@ checkmailpath(char **s)
 /**/
 FILE *xtrerr = 0;
 
+/* This records the last file XTRACE was open too.
+ * It's used for restoring XTRACE after a possible redirection.
+ */
+
+/**/
+FILE *xtrace_file;
+
 /**/
 void
 printprompt4(void)
 {
     if (!xtrerr)
-	xtrerr = stderr;
+	xtracefdassign();
     if (prompt4) {
 	int l, t = opts[XTRACE];
 	char *s = dupstring(prompt4);

Test/A04redirect.ztst

@@ -721,3 +721,70 @@
 >Works
 >Works
 ?(eval):6: file exists: foo
+
+  rm -f redir
+  set -x
+  ZSH_XTRACEFD=4 print 'This is ZSH_XTRACEFD redir' 4>redir
+  set +x
+  cat redir
+0:Redirect xtrace output to ZSH_XTRACEFD file descriptor
+>This is ZSH_XTRACEFD redir
+>+(eval):3> print 'This is ZSH_XTRACEFD redir'
+?+(eval):3> ZSH_XTRACEFD=4 +(eval):4> set +x
+
+  rm -f redir
+  A() {
+    local ZSH_XTRACEFD=5
+    B
+    print 'Function A to file descriptor 5'
+    unset ZSH_XTRACEFD
+    print 'Function A to file descriptor 2'
+  }
+  B() {
+    local ZSH_XTRACEFD=6
+    print 'Function B to file descriptor 6'
+  }
+  exec 4>redir4 5>redir5 6>redir6
+  ZSH_XTRACEFD=4
+  set -x
+  print 'Main to file descriptor 4'
+  A
+  print 'Main to file descriptor 4 again\n'
+  a=0 ZSH_XTRACEFD=5  # appears as blank line in redir5
+  ZSH_XTRACEFD=6  # appears as blank line in redir6
+  unset ZSH_XTRACEFD
+  set +x
+  print "end of file redir4" >> redir4
+  cat redir4
+  print
+  print "end of file redir5" >> redir5
+  cat redir5
+  print
+  print "end of file redir6" >> redir6
+  cat redir6
+0:Scoped ZSH_XTRACEFD correctly set and restored
+>Main to file descriptor 4
+>Function B to file descriptor 6
+>Function A to file descriptor 5
+>Function A to file descriptor 2
+>Main to file descriptor 4 again
+>
+>+(eval):16> print 'Main to file descriptor 4'
+>+(eval):17> A
+>+A:1> local ZSH_XTRACEFD=5
+>+(eval):18> print 'Main to file descriptor 4 again\n'
+>end of file redir4
+>
+>+A:2> B
+>+B:1> local ZSH_XTRACEFD=6
+>+A:3> print 'Function A to file descriptor 5'
+>+A:4> unset ZSH_XTRACEFD
+>
+>end of file redir5
+>
+>+B:2> print 'Function B to file descriptor 6'
+>
+>+(eval):21> unset ZSH_XTRACEFD
+>end of file redir6
+?+A:5> print 'Function A to file descriptor 2'
+?+(eval):22> set +x