Ninja: Generate scripts for long custom command sequences

Ninja runs just one command line for every build statement, so the Ninja
generator needs to `&&`-chain multiple commands together into one long
string.  For long custom command sequences this can exceed the maximum
command-line length for the operating system.  In such cases, write the
commands out to a script instead, and then run the script from Ninja's
one command line.

Co-Author: Brad King <brad.king@kitware.com>
Fixes: #15612

2 files changed, 21 insertions, 0 deletions

diff --git a/Tests/CommandLength/CMakeLists.txt b/Tests/CommandLength/CMakeLists.txt
new file mode 100644
index 0000000..6836051
--- /dev/null
+++ b/Tests/CommandLength/CMakeLists.txt
@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.10)
+project(CommandLength C)
+
+add_executable(CommandLength test.c)
+add_custom_command(TARGET CommandLength POST_BUILD VERBATIM
+  COMMAND ${CMAKE_COMMAND} -E make_directory log)
+
+set(msg "xxxx $$$$ yyyy")
+set(msg "${msg} ${msg}")
+set(msg "${msg} ${msg}")
+set(msg "${msg} ${msg}")
+set(msg "${msg} ${msg}")
+foreach(i RANGE 1 1000)
+  add_custom_command(TARGET CommandLength POST_BUILD VERBATIM
+    COMMAND ${CMAKE_COMMAND} -E echo "${i} ${msg}" > log/${i}
+    )
+endforeach()
diff --git a/Tests/CommandLength/test.c b/Tests/CommandLength/test.c
new file mode 100644
index 0000000..f8b643a
--- /dev/null
+++ b/Tests/CommandLength/test.c
@@ -0,0 +1,4 @@
+int main()
+{
+  return 0;
+}