blob2xex: warn on address wraparound.

3 files changed, 68 insertions, 13 deletions

diff --git a/blob2xex.1 b/blob2xex.1
index 0780513..ee00503 100644
--- a/blob2xex.1
+++ b/blob2xex.1
@@ -117,14 +117,40 @@ Print version number and exit.
 .sp
 Error messages and warnings are printed to standard error, and are
 hopefully self\-explanatory. Any message containing \fIfatal\fP causes
-\fBblob2xex\fP to exit without creating the output file.
+\fBblob2xex\fP to exit with nonzero status, without creating the output
+file.
 .sp
 Messages containing \fIwarning\fP are non\-fatal, and the output file is
-created. The only warning messages are there to let you know if your
-\&.xex file\(aqs start/end addresses mean it would load into ROM (or, the
-unmapped area at \fB$C000\fP on a 400/800). Normally this means the .xex
-file won\(aqt load properly on the Atari, but feel free to ignore the
-warnings if you know exactly what you\(aqre doing.
+created. There are only a few possible warnings:
+.INDENT 0.0
+.INDENT 3.5
+.INDENT 0.0
+.TP
+.B start/end address XXXX loads into ROM.
+This means your .exe file\(aqs start/end addresses will load the
+file into ROM (or the unmapped area at \fB$C000\fP on a 400/800).
+Normally this means the .xex file won\(aqt load properly on the
+Atari, but feel free to ignore this warning if you know exactly
+what you\(aqre doing.
+.TP
+.B address would exceed $FFFF! truncated N bytes to N.
+The segment would wrap around the Atari\(aqs 64KB address space.
+\fBblob2xex\fP has truncated the input so the last address
+loaded is \fB$FFFF\fP\&. This warning usually means you gave the
+wrong load address or the wrong input file entirely.
+.TP
+.B extra arguments after last input file ignored.
+You gave at least one option that would affect the next file,
+after the last file on the command line. Such options are ignored,
+since there\(aqs no file for them to apply to. Probably you made
+a typo or forgot the last input file.
+.UNINDENT
+.UNINDENT
+.UNINDENT
+.SH EXIT STATUS
+.sp
+Zero for success (the output file was created), even if there were
+warnings. Non\-zero for failure (the output file wasn\(aqt created).
 .SH EXAMPLES
 .SS Simple Example
 .sp
diff --git a/blob2xex.c b/blob2xex.c
index 0f17371..413fb52 100644
--- a/blob2xex.c
+++ b/blob2xex.c
@@ -99,8 +99,12 @@ int write_segment(
 	}
 
 	/* make sure we don't wrap the Atari's address space. */
-	if(size + loadaddr > 0xffff)
+	if(size + loadaddr > 0xffff) {
+		int oldsize = size;
 		size = (size - loadaddr) + 1;
+		fprintf(stderr, SELF ": "
+				"warning: %s: address would exceed $FFFF! truncated %d bytes to %d.\n", infile, oldsize, size);
+	}
 
 	/* read <size> bytes, or until EOF (which is not an error) */
 	while(size) {
@@ -209,6 +213,7 @@ int main(int argc, char **argv) {
 			if( (bytes = write_segment(infile, outfile, loadaddr, initaddr, offset, size)) ) {
 				segcount++;
 				loadaddr += bytes;
+				loadaddr %= 0xffff;
 			} else {
 				segcount = 0;
 				break;
@@ -245,6 +250,8 @@ int main(int argc, char **argv) {
 			fprintf(stderr, SELF ": read %d input files, wrote %d segments to %s.\n",
 					incount, segcount, outfile);
 	} else {
+		if(xex_verbose)
+			fprintf(stderr, SELF ": no output file created, due to fatal error.\n");
 		unlink(outfile);
 		return 1;
 	}
diff --git a/blob2xex.rst b/blob2xex.rst
index a3161ab..9984b2b 100644
--- a/blob2xex.rst
+++ b/blob2xex.rst
@@ -97,14 +97,36 @@ DIAGNOSTICS
 
 Error messages and warnings are printed to standard error, and are
 hopefully self-explanatory. Any message containing *fatal* causes
-**blob2xex** to exit without creating the output file.
+**blob2xex** to exit with nonzero status, without creating the output
+file.
 
 Messages containing *warning* are non-fatal, and the output file is
-created. The only warning messages are there to let you know if your
-.xex file's start/end addresses mean it would load into ROM (or, the
-unmapped area at **$C000** on a 400/800). Normally this means the .xex
-file won't load properly on the Atari, but feel free to ignore the
-warnings if you know exactly what you're doing.
+created. There are only a few possible warnings:
+
+  start/end address XXXX loads into ROM.
+    This means your .exe file's start/end addresses will load the
+    file into ROM (or the unmapped area at **$C000** on a 400/800).
+    Normally this means the .xex file won't load properly on the
+    Atari, but feel free to ignore this warning if you know exactly
+    what you're doing.
+
+  address would exceed $FFFF! truncated N bytes to N.
+    The segment would wrap around the Atari's 64KB address space.
+    **blob2xex** has truncated the input so the last address
+    loaded is **$FFFF**. This warning usually means you gave the
+    wrong load address or the wrong input file entirely.
+
+  extra arguments after last input file ignored.
+    You gave at least one option that would affect the next file,
+    after the last file on the command line. Such options are ignored,
+    since there's no file for them to apply to. Probably you made
+    a typo or forgot the last input file.
+
+EXIT STATUS
+===========
+
+Zero for success (the output file was created), even if there were
+warnings. Non-zero for failure (the output file wasn't created).
 
 EXAMPLES
 ========