From 28442e60b84c7eacfd02079e1857b042f06c0150 Mon Sep 17 00:00:00 2001
From: Colin Leroy-Mira <colin@colino.net>
Date: Sun, 19 Oct 2025 11:14:45 +0200
Subject: [PATCH 1/2] Emit warnings for wasted bytes when aligning

---
 doc/ca65.sgml       | 3 ++-
 src/ca65/segment.c  | 4 +++-
 src/ld65/config.c   | 4 ++--
 src/ld65/segments.c | 3 +++
 4 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/doc/ca65.sgml b/doc/ca65.sgml
index 40231920c..af5e73d13 100644
--- a/doc/ca65.sgml
+++ b/doc/ca65.sgml
@@ -2372,7 +2372,8 @@ Here's a list of all control commands and a description, what they do:
   calculated in advance by the assembler. You are therefore required to
   specify a matching alignment for the segment in the linker config. The
   linker will output a warning if the alignment of the segment is less than
-  what is necessary to have a correct alignment in the object file.
+  what is necessary to have a correct alignment in the object file. It will
+  also emit a warning to inform about the number of bytes wasted for alignment.
 
   Example:
 
diff --git a/src/ca65/segment.c b/src/ca65/segment.c
index adc5cec98..76126d23d 100644
--- a/src/ca65/segment.c
+++ b/src/ca65/segment.c
@@ -313,7 +313,9 @@ void SegAlign (unsigned long Alignment, int FillVal)
 
         /* Calculate the number of fill bytes */
         Count = AlignCount (ActiveSeg->PC, Alignment);
-
+        if (Count != 0) {
+            Warning(0, "Wasting %lu bytes for alignment", Count);
+        }
     }
 
 
diff --git a/src/ld65/config.c b/src/ld65/config.c
index bc2a26578..9536d5c26 100644
--- a/src/ld65/config.c
+++ b/src/ld65/config.c
@@ -2035,8 +2035,8 @@ unsigned CfgProcess (void)
                     if (M->FillLevel == 0 && NewAddr > Addr) {
                         PWarning (GetSourcePos (S->LI),
                                   "The first segment in memory area `%s' "
-                                  "needs fill bytes for alignment.",
-                                  GetString (M->Name));
+                                  "needs %lu fill bytes for alignment.",
+                                  GetString (M->Name), NewAddr - Addr);
                     }
 
                     /* Use the aligned address */
diff --git a/src/ld65/segments.c b/src/ld65/segments.c
index 1391d30f1..aeff972d2 100644
--- a/src/ld65/segments.c
+++ b/src/ld65/segments.c
@@ -236,6 +236,9 @@ Section* ReadSection (FILE* F, ObjData* O)
                      GetString (Name), Alignment, GetObjFileName (O));
         }
         S->Alignment = Alignment;
+        if (Sec->Fill != 0) {
+            Warning("Wasting %lu bytes for alignment from %s", Sec->Fill, GetObjFileName (O));
+        }
     }
 
     /* Start reading fragments from the file and insert them into the section . */

From 2220c6ec8dd4dc5ba497e8e783e15f4b305737eb Mon Sep 17 00:00:00 2001
From: Colin Leroy-Mira <colin@colino.net>
Date: Sun, 26 Oct 2025 16:06:08 +0100
Subject: [PATCH 2/2] Add --warn-align-waste option to ca65, ld65, cl65

---
 doc/ca65.sgml       |  8 ++++++++
 doc/cl65.sgml       |  2 ++
 doc/ld65.sgml       |  9 +++++++++
 src/ca65/global.c   |  1 +
 src/ca65/global.h   |  1 +
 src/ca65/main.c     | 11 +++++++++++
 src/ca65/segment.c  |  2 +-
 src/cl65/main.c     | 16 ++++++++++++++--
 src/ld65/global.c   |  1 +
 src/ld65/global.h   |  1 +
 src/ld65/main.c     | 14 +++++++++++++-
 src/ld65/segments.c |  5 +++--
 12 files changed, 65 insertions(+), 6 deletions(-)

diff --git a/doc/ca65.sgml b/doc/ca65.sgml
index af5e73d13..4e42d0c05 100644
--- a/doc/ca65.sgml
+++ b/doc/ca65.sgml
@@ -133,6 +133,7 @@ Long options:
   --target sys                  Set the target system
   --verbose                     Increase verbosity
   --version                     Print the assembler version
+  --warn-align-waste            Print bytes "wasted" for alignment
   --warnings-as-errors          Treat warnings as errors
 ---------------------------------------------------------------------------
 </verb></tscreen>
@@ -407,6 +408,13 @@ Here is a description of all the command line options:
   something lower.
 
 
+  <label id="option--warn-align-waste">
+  <tag><tt>--warn-align-waste</tt></tag>
+
+  Warnings will be generated when alignment requirements cause emission of
+  fill bytes.
+
+
   <label id="option--warnings-as-errors">
   <tag><tt>--warnings-as-errors</tt></tag>
 
diff --git a/doc/cl65.sgml b/doc/cl65.sgml
index 8413db6c0..74a3cada8 100644
--- a/doc/cl65.sgml
+++ b/doc/cl65.sgml
@@ -119,6 +119,8 @@ Long options:
   --target sys                  Set the target system
   --version                     Print the version number
   --verbose                     Verbose mode
+  --warn-align-waste            Print bytes "wasted" for alignment
+  --warnings-as-errors          Treat warnings as errors
   --zeropage-label name         Define and export a ZEROPAGE segment label
   --zeropage-name seg           Set the name of the ZEROPAGE segment
 ---------------------------------------------------------------------------
diff --git a/doc/ld65.sgml b/doc/ld65.sgml
index 8a4ceca43..3426af4be 100644
--- a/doc/ld65.sgml
+++ b/doc/ld65.sgml
@@ -92,6 +92,8 @@ Long options:
   --start-group                 Start a library group
   --target sys                  Set the target system
   --version                     Print the linker version
+  --warn-align-waste            Print bytes "wasted" for alignment
+  --warnings-as-errors          Treat warnings as errors
 ---------------------------------------------------------------------------
 </verb></tscreen>
 
@@ -349,6 +351,13 @@ Here is a description of all of the command-line options:
   directories given by environment variables, and in a built-in default directory.
 
 
+  <label id="option--warn-align-waste">
+  <tag><tt>--warn-align-waste</tt></tag>
+
+  Warnings will be generated when alignment requirements cause emission of
+  fill bytes.
+
+
   <label id="option--warnings-as-errors">
   <tag><tt>--warnings-as-errors</tt></tag>
 
diff --git a/src/ca65/global.c b/src/ca65/global.c
index 1398ce2c7..50291be63 100644
--- a/src/ca65/global.c
+++ b/src/ca65/global.c
@@ -68,6 +68,7 @@ unsigned char LargeAlignment     = 0;   /* Don't warn about large alignments */
 unsigned char RelaxChecks        = 0;   /* Relax a few assembler checks */
 unsigned char StringEscapes      = 0;   /* Allow C-style escapes in strings */
 unsigned char LongJsrJmpRts      = 0;   /* Allow JSR/JMP/RTS as alias for JSL/JML/RTL */
+unsigned char WarnAlignWaste     = 0;   /* Warn about "wasted" bytes when aligning */
 unsigned char WarningsAsErrors   = 0;   /* Error if any warnings */
 unsigned char SegList            = 0;   /* Show segments in listing */
 unsigned char ExpandMacros       = 0;   /* Expand macros in listing */
diff --git a/src/ca65/global.h b/src/ca65/global.h
index 1923bc748..41c37bbcb 100644
--- a/src/ca65/global.h
+++ b/src/ca65/global.h
@@ -70,6 +70,7 @@ extern unsigned char    LargeAlignment;     /* Don't warn about large alignments
 extern unsigned char    RelaxChecks;        /* Relax a few assembler checks */
 extern unsigned char    StringEscapes;      /* Allow C-style escapes in strings */
 extern unsigned char    LongJsrJmpRts;      /* Allow JSR/JMP/RTS as alias for JSL/JML/RTL */
+extern unsigned char    WarnAlignWaste;     /* Warn about "wasted" bytes when aligning */
 extern unsigned char    WarningsAsErrors;   /* Error if any warnings */
 extern unsigned char    SegList;            /* Show segments in listing */
 extern unsigned char    ExpandMacros;       /* Expand macros in listing */
diff --git a/src/ca65/main.c b/src/ca65/main.c
index 66ba331dd..efaedc907 100644
--- a/src/ca65/main.c
+++ b/src/ca65/main.c
@@ -138,6 +138,7 @@ static void Usage (void)
             "  --target sys\t\t\tSet the target system\n"
             "  --verbose\t\t\tIncrease verbosity\n"
             "  --version\t\t\tPrint the assembler version\n"
+            "  --warn-align-waste\t\tPrint bytes \"wasted\" for alignment\n"
             "  --warnings-as-errors\t\tTreat warnings as errors\n",
             ProgName);
 }
@@ -753,6 +754,15 @@ static void OptSeglist (const char* Opt attribute ((unused)),
 
 
 
+static void OptWarnAlignWaste (const char* Opt attribute ((unused)),
+                               const char* Arg attribute ((unused)))
+/* Warn about bytes "wasted" for alignment */
+{
+    WarnAlignWaste = 1;
+}
+
+
+
 static void OptWarningsAsErrors (const char* Opt attribute ((unused)),
                                  const char* Arg attribute ((unused)))
 /* Generate an error if any warnings occur */
@@ -1091,6 +1101,7 @@ int main (int argc, char* argv [])
         { "--target",              1,      OptTarget               },
         { "--verbose",             0,      OptVerbose              },
         { "--version",             0,      OptVersion              },
+        { "--warn-align-waste",    0,      OptWarnAlignWaste       },
         { "--warnings-as-errors",  0,      OptWarningsAsErrors     },
     };
 
diff --git a/src/ca65/segment.c b/src/ca65/segment.c
index 76126d23d..d5073895d 100644
--- a/src/ca65/segment.c
+++ b/src/ca65/segment.c
@@ -313,7 +313,7 @@ void SegAlign (unsigned long Alignment, int FillVal)
 
         /* Calculate the number of fill bytes */
         Count = AlignCount (ActiveSeg->PC, Alignment);
-        if (Count != 0) {
+        if (WarnAlignWaste && Count != 0) {
             Warning(0, "Wasting %lu bytes for alignment", Count);
         }
     }
diff --git a/src/cl65/main.c b/src/cl65/main.c
index 3339ebda1..0f30b4855 100644
--- a/src/cl65/main.c
+++ b/src/cl65/main.c
@@ -897,9 +897,10 @@ static void Usage (void)
             "  --target sys\t\t\tSet the target system\n"
             "  --version\t\t\tPrint the version number\n"
             "  --verbose\t\t\tVerbose mode\n"
+            "  --warn-align-waste\t\tPrint bytes \"wasted\" for alignment\n"
+            "  --warnings-as-errors\t\tTreat warnings as errors\n"
             "  --zeropage-label name\t\tDefine and export a ZEROPAGE segment label\n"
-            "  --zeropage-name seg\t\tSet the name of the ZEROPAGE segment\n"
-            "  --warnings-as-errors\t\tTreat warnings as errors\n",
+            "  --zeropage-name seg\t\tSet the name of the ZEROPAGE segment\n",
             ProgName);
 }
 
@@ -1436,6 +1437,16 @@ static void OptZeropageName (const char* Opt attribute ((unused)), const char* A
 
 
 
+static void OptWarnAlignWaste (const char* Opt attribute ((unused)),
+                               const char* Arg attribute ((unused)))
+/* Handle the --warn-align-waste option */
+{
+    CmdAddArg (&CA65, "--warn-align-waste");
+    CmdAddArg (&LD65, "--warn-align-waste");
+}
+
+
+
 static void OptWarningsAsErrors (const char* Opt attribute ((unused)),
                                  const char* Arg attribute ((unused)))
 /* Handle the --warnings-as-errors option */
@@ -1506,6 +1517,7 @@ int main (int argc, char* argv [])
         { "--version",             0, OptVersion            },
         { "--zeropage-label",      1, OptZeropageLabel      },
         { "--zeropage-name",       1, OptZeropageName       },
+        { "--warn-align-waste",    0, OptWarnAlignWaste     },
         { "--warnings-as-errors",  0, OptWarningsAsErrors   },
     };
 
diff --git a/src/ld65/global.c b/src/ld65/global.c
index 93dd65958..a7c81891a 100644
--- a/src/ld65/global.c
+++ b/src/ld65/global.c
@@ -55,6 +55,7 @@ unsigned long StartAddr         = 0x200;    /* Start address */
 unsigned char VerboseMap        = 0;        /* Verbose map file */
 unsigned char AllowMultDef      = 0;        /* Allow multiple definitions */
 unsigned char LargeAlignment    = 0;        /* Don't warn about large alignments */
+unsigned char WarnAlignWaste    = 0;        /* Warn about "wasted" bytes when aligning */
 unsigned char WarningsAsErrors  = 0;        /* Error if any warnings */
 
 const char* MapFileName         = 0;        /* Name of the map file */
diff --git a/src/ld65/global.h b/src/ld65/global.h
index ad85daf0a..983f25f7e 100644
--- a/src/ld65/global.h
+++ b/src/ld65/global.h
@@ -55,6 +55,7 @@ extern unsigned long    StartAddr;         /* Start address */
 extern unsigned char    VerboseMap;        /* Verbose map file */
 extern unsigned char    AllowMultDef;      /* Allow multiple definitions */
 extern unsigned char    LargeAlignment;    /* Don't warn about large alignments */
+extern unsigned char    WarnAlignWaste;    /* Warn about "wasted" bytes when aligning */
 extern unsigned char    WarningsAsErrors;  /* Error if any warnings */
 
 extern const char*      MapFileName;       /* Name of the map file */
diff --git a/src/ld65/main.c b/src/ld65/main.c
index 3b434f68d..9865f1dbf 100644
--- a/src/ld65/main.c
+++ b/src/ld65/main.c
@@ -179,7 +179,9 @@ static void Usage (void)
             "  --start-addr addr\t\tSet the default start address\n"
             "  --start-group\t\t\tStart a library group\n"
             "  --target sys\t\t\tSet the target system\n"
-            "  --version\t\t\tPrint the linker version\n",
+            "  --version\t\t\tPrint the linker version\n"
+            "  --warn-align-waste\t\tPrint bytes \"wasted\" for alignment\n"
+            "  --warnings-as-errors\t\tTreat warnings as errors\n",
             ProgName);
 }
 
@@ -608,6 +610,15 @@ static void OptVersion (const char* Opt attribute ((unused)),
 
 
 
+static void OptWarnAlignWaste (const char* Opt attribute ((unused)),
+                               const char* Arg attribute ((unused)))
+/* Warn about bytes "wasted" for alignment */
+{
+    WarnAlignWaste = 1;
+}
+
+
+
 static void OptWarningsAsErrors (const char* Opt attribute ((unused)),
                                  const char* Arg attribute ((unused)))
 /* Generate an error if any warnings occur */
@@ -691,6 +702,7 @@ static void ParseCommandLine (void)
         { "--start-group",               0,      CmdlOptStartGroup       },
         { "--target",                    1,      CmdlOptTarget           },
         { "--version",                   0,      OptVersion              },
+        { "--warn-align-waste",          0,      OptWarnAlignWaste       },
         { "--warnings-as-errors",        0,      OptWarningsAsErrors     },
     };
 
diff --git a/src/ld65/segments.c b/src/ld65/segments.c
index aeff972d2..8ef9dc107 100644
--- a/src/ld65/segments.c
+++ b/src/ld65/segments.c
@@ -236,8 +236,9 @@ Section* ReadSection (FILE* F, ObjData* O)
                      GetString (Name), Alignment, GetObjFileName (O));
         }
         S->Alignment = Alignment;
-        if (Sec->Fill != 0) {
-            Warning("Wasting %lu bytes for alignment from %s", Sec->Fill, GetObjFileName (O));
+        if (WarnAlignWaste && Sec->Fill != 0) {
+            Warning("%s: Wasting %lu bytes for `%s' alignment",
+                    GetObjFileName (O), Sec->Fill, GetString (Name));
         }
     }