From 835bc129356e2cfd15109b53e41042fd52f622aa Mon Sep 17 00:00:00 2001
From: ZainnQureshii <43629888+ZainnQureshii@users.noreply.github.com>
Date: Tue, 10 Nov 2026 20:58:22 +0100
Subject: [PATCH] cli: fix --memlimit-decompress= argument parsing

longCommandWArg() matches by prefix, and the --memlimit branch came
before --memlimit-decompress, so --memlimit-decompress=8M matched
--memlimit and left "-decompress=8M" for NEXT_UINT32, which then read
the next argument as the value. Check the longer alias first, and add a
CLI test for all three spellings in both argument forms.
---
 programs/zstdcli.c                                |  2 +-
 tests/cli-tests/basic/memlimit_alias.sh           | 15 +++++++++++++++
 .../basic/memlimit_alias.sh.stderr.exact          |  0
 .../basic/memlimit_alias.sh.stdout.exact          |  0
 4 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100755 tests/cli-tests/basic/memlimit_alias.sh
 create mode 100644 tests/cli-tests/basic/memlimit_alias.sh.stderr.exact
 create mode 100644 tests/cli-tests/basic/memlimit_alias.sh.stdout.exact

diff --git a/programs/zstdcli.c b/programs/zstdcli.c
index d0821db9741..2247ab9d686 100644
--- a/programs/zstdcli.c
+++ b/programs/zstdcli.c
@@ -1102,9 +1102,9 @@ int main(int argCount, const char* argv[])
                 }
 #endif
                 if (longCommandWArg(&argument, "--threads")) { NEXT_UINT32(nbWorkers); setThreads_non1 = (nbWorkers != 1); continue; }
+                if (longCommandWArg(&argument, "--memlimit-decompress")) { NEXT_UINT32(memLimit); continue; }
                 if (longCommandWArg(&argument, "--memlimit")) { NEXT_UINT32(memLimit); continue; }
                 if (longCommandWArg(&argument, "--memory")) { NEXT_UINT32(memLimit); continue; }
-                if (longCommandWArg(&argument, "--memlimit-decompress")) { NEXT_UINT32(memLimit); continue; }
                 if (longCommandWArg(&argument, "--block-size")) { NEXT_TSIZE(chunkSize); continue; } /* hidden command, prefer --split below */
                 if (longCommandWArg(&argument, "--split")) { NEXT_TSIZE(chunkSize); continue; }
                 if (longCommandWArg(&argument, "--jobsize")) { NEXT_TSIZE(chunkSize); continue; } /* note: overloaded variable */
diff --git a/tests/cli-tests/basic/memlimit_alias.sh b/tests/cli-tests/basic/memlimit_alias.sh
new file mode 100755
index 00000000000..60b22733d7d
--- /dev/null
+++ b/tests/cli-tests/basic/memlimit_alias.sh
@@ -0,0 +1,15 @@
+#!/bin/sh
+set -eu
+
+datagen -g500K > input
+zstd -q input
+for option in --memlimit --memory --memlimit-decompress; do
+    zstd -dc "$option=8M" input.zst > output
+    cmp input output
+    zstd -dc "$option" 8M input.zst > output
+    cmp input output
+    if zstd -qdc "$option=1K" input.zst > output 2> error; then
+        die "Decompression exceeded the memory limit"
+    fi
+    grep -q 'Window size larger than maximum' error
+done
diff --git a/tests/cli-tests/basic/memlimit_alias.sh.stderr.exact b/tests/cli-tests/basic/memlimit_alias.sh.stderr.exact
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/cli-tests/basic/memlimit_alias.sh.stdout.exact b/tests/cli-tests/basic/memlimit_alias.sh.stdout.exact
new file mode 100644
index 00000000000..e69de29bb2d