Using Delphi's command line compiler dcc64.exe, I wonder what the option -M does. It is documented as Make modified units, which does not make enough sense to me. Also, what is the corresponding checkbox in the Delphi options dialog?
I cannot find any more in-depth documentation of these compiler options. Here's the default output of the compiler:
Embarcadero Delphi for Win64 compiler version 35.0
Copyright (c) 1983,2022 Embarcadero Technologies, Inc.
Syntax: dcc64 [options] filename [options]
-A<unit>=<alias> = Set unit alias
-B = Build all units
-CC = Console target
-CG = GUI target
-D<syms> = Define conditionals
-E<path> = EXE/DLL output directory
-F<offset> = Find error
-GD = Detailed map file
-GP = Map file with publics
-GS = Map file with segments
-H = Output hint messages
-I<paths> = Include directories
-J = Generate .obj file
-JPHNE = Generate C++ .obj file, .hpp file, in namespace, export all
-JL = Generate package .lib, .bpi, and all .hpp files for C++
-K<addr> = Set image base addr
-LE<path> = package .bpl output directory
-LN<path> = package .dcp output directory
-LU<package> = Use package
-M = Make modified units
-NU<path> = unit .dcu output directory
-NH<path> = unit .hpp output directory
-NO<path> = unit .obj output directory
-NB<path> = unit .bpi output directory
-NX<path> = unit .xml output directory
-NS<namespaces> = Namespace search path
-O<paths> = Object directories
-P = look for 8.3 file names also
-Q = Quiet compile
-R<paths> = Resource directories
-TX<ext> = Output name extension
-U<paths> = Unit directories
-V = Debug information in EXE
-VR = Generate remote debug (RSM)
-VT = Debug information in TDS
-VN = TDS symbols in namespace
-W[+|-|^][warn_id] = Output warning messages
-Z = Output 'never build' DCPs
-$<dir> = Compiler directive
--help = Show this help screen
--version = Show name and version
--codepage:<cp> = specify source file encoding
--default-namespace:<namespace> = set namespace
--depends = output unit dependency information
--doc = output XML documentation
--drc = output resource string .drc file
--no-config = do not load default dcc64.cfg file
--description:<string> = set executable description
--inline:{on|off|auto} = function inlining control
--legacy-ifend = allow legacy $IFEND directive
--zero-based-strings[+|-] = strings are indexed starting at 0
--peflags:<flags> = set extra PE Header flags field
--peoptflags:<flags> = set extra PE Header optional flags field
--peosversion:<major>.<minor> = set OS Version fields in PE Header (default: 5.0)
--pesubsysversion:<major>.<minor> = set Subsystem Version fields in PE Header (default: 5.0)
--peuserversion:<major>.<minor> = set User Version fields in PE Header (default: 0.0)
--lib-version:<version> = Output package name version
--lib-suffix:<suffix> = Output package name suffix
Compiler switches: -$<letter><state> (defaults are shown below)
A8 Aligned record fields
B- Full boolean Evaluation
C+ Evaluate assertions at runtime
D+ Debug information
G+ Use imported data references
H+ Use long strings by default
I+ I/O checking
J- Writeable structured consts
L+ Local debug symbols
M- Runtime type info
O+ Optimization
P+ Open string params
Q- Integer overflow checking
R- Range checking
T- Typed @ operator
V+ Strict var-strings
W- Generate stack frames
X+ Extended syntax
Y+ Symbol reference info
Z1 Minimum size of enum types
Stack size: -$M<minStackSize[,maxStackSize]> (default 16384,1048576)
With basic words.
Main diffrence between them
"-M" (Compile) is incremental build consider only units changes, so much faster. elseway the compiler will start build every unit from scratch usable on releases and in some cases compiling issues