mql-compiler

Compile MQL4 (.mq4) and MQL5 (.mq5) sources to .ex4/.ex5 on Linux with the mql-compiler command, and read its compile errors.

mql-compiler compiles MetaTrader sources with MetaQuotes' own MetaEditor, running under Wine in the psyb0t/mql-compiler Docker image. It needs Docker on an x86-64 (amd64) machine and nothing else: no Windows, no MetaTrader terminal, no trading account. There is no ARM image.

Install

If mql-compiler is not on PATH, install it for the current user:

bash

curl -fsSL https://raw.githubusercontent.com/psyb0t/docker-mql-compiler/master/install.sh | bash

It lands in ~/.local/bin; if that is not on PATH, the installer prints the line to add. For system-wide installs, upgrades, uninstalling, custom installers and troubleshooting, see references/installation.md.

Compile

bash

mql-compiler [FILE or FOLDER ...]

mql-compiler                                # every .mq4 and .mq5 under the current folder
mql-compiler /abs/path/MQL5/Experts/Foo.mq5 # one file, from any folder
mql-compiler MQL5/Indicators MQL4           # folders, searched recursively

• Arguments are files or folders, relative or absolute, anywhere on the machine. No argument means the current folder. No cd is needed. A path that does not exist stops the run with exit 2 before anything compiles.
• A folder is searched recursively for .mq4 and .mq5 (any case), sorted by path; symlinked files inside it are skipped. Arguments are handled in the order given; a file named twice compiles once, in its first position. .mqh and other files are skipped in folders and rejected (exit 2) when named directly. A run that finds no sources exits 2.
• One container runs the whole list, one file at a time, never in parallel. A failing file does not stop the run. Pass everything to one call: two runs at the same time take turns (the second logs that it is waiting), so splitting a job only makes it slower.
• Paths with spaces work; the messages still show the real paths.
• The extension alone picks the compiler: .mq4 goes to MT4's MetaEditor, .mq5 to MT5's. The folder only decides the includes: a .mq4 uses the nearest folder named MQL4 (any case) above it, a .mq5 the nearest MQL5. Experts, indicators, scripts and libraries all compile the same way.
• Each .ex4/.ex5 is written next to its source with the same base name, owned by the caller. The old one is deleted right before the file compiles, so after a run an .ex4/.ex5 exists only if this run produced it. Still report success from the file's OK line.
• The container sees only the mounted folders (each source's MQL4/MQL5 folder, or a loose file's own folder). Includes, resources and symlinks that point outside them are missing files inside the container.
• The first run downloads and installs MT4 and MT5 into the mql-compiler-cache Docker volume and unpacks their standard libraries, about a minute and a half. Allow for it in timeouts; later runs take seconds. mql-compiler --setup does only this.

How includes resolve

• #include <...> searches one merged folder built for the run: the matching platform's MetaQuotes standard library (<Trade/Trade.mqh>, <Arrays/ArrayObj.mqh>, <stdlib.mqh>, ...) with the Include folder of the nearest enclosing MQL4 (for .mq4) or MQL5 (for .mq5) folder laid over it. When both have the same path, the user's file wins.
• #resource "\\Files\\x.txt" and other \\-rooted paths start at that same MQL4/MQL5 folder.
• #include "..." resolves next to the source.
• A source outside any MQL4/MQL5 folder gets the standard library only, and no \\-rooted resources.
• An error inside a standard header is reported at the header's path in the toolchain (/cache/uid-<UID>/wine/drive_c/..., inside the cache volume, not on the host). It usually means the user's code broke something the header relies on, such as a macro with the same name as a standard class; fix the user's code, never the toolchain.
• Nothing is written into the user's folders or the toolchain; the merged folder is temporary.

So keep a terminal-style tree: sources under MQL5/Experts, MQL5/Indicators, ..., headers under MQL5/Include (same for MQL4). When copying a source elsewhere to compile it, copy its MQL4/MQL5 folder with it, or its custom includes go missing.

Read the result

Results go to stdout, one line per file, followed by that file's compiler messages:

text

OK   MQL5/Experts/Foo.mq5 -> MQL5/Experts/Foo.ex5 (0 warnings)
FAIL MQL5/Experts/Bar.mq5 (1 errors, 0 warnings)
     MQL5/Experts/Bar.mq5(41,7) : error 256: undeclared identifier 'lots'

Errors read path(line,column) : error <code>: <message>. Paths are relative to the current folder when inside it, absolute otherwise. Fix the source at that line and compile again. Progress and diagnostics go to stderr as JSON lines; 2>/dev/null hides them. A copy of the last run (stdout and stderr) is in the cache volume: docker run --rm -v mql-compiler-cache:/c busybox cat /c/uid-$(id -u)/logs/last-run.log.

Exit	Meaning
0	Every file compiled
1	At least one file has compile errors, or MetaEditor wrote no result for it (see the FAIL lines)
2	Bad path or option, no sources found, or the toolchain could not be set up (see stderr)
125 and other Docker codes	Docker itself failed: daemon down, image not pullable, a bad mount

Rules for agents

• Use the mql-compiler command. Do not build your own docker run unless the user asks.
• Report compile errors with their file, line and message. A file compiled when its line says OK, even if the run exits 1 because of another file. Claim the whole build succeeded only when the exit status is 0.
• file '...' not found on an #include <...> means the header is in neither the user's Include nor the standard library. Check the source sits under the right MQL4/MQL5 folder before editing code.
• MQL_COMPILER_MT4_URL and MQL_COMPILER_MT5_URL choose other installers, which only matters on a first run, so pair them with a fresh MQL_COMPILER_VOLUME. Remove a volume only when the user asks: it costs another full download, and mql-compiler-cache holds every user's toolchain on the machine.