[olantwin]

The CMake build can't currently be cross-compiled. stdlib/CMakeLists.txt generates std.jsonnet.h by building to_c_array and running it on std.jsonnet. When cross-compiling, to_c_array is a target binary, so the custom command fails with exit code 127 on the build machine. We hit this adding linux-aarch64 and osx-arm64 builds to conda-forge's libjsonnet
package (conda-forge/libjsonnet-feedstock#2), which cross-compiles both.

With this change, when CMAKE_CROSSCOMPILING is set, CMake reads std.jsonnet as hex at configure time and writes the header itself, in the same layout to_c_array produces: comma-separated byte values followed by a terminating 0. It writes the bytes as hex literals instead of decimal, but the values are the same. std.jsonnet is listed in CMAKE_CONFIGURE_DEPENDS, so editing it still regenerates the header. Native builds keep using
to_c_array and are unchanged.

This approach doesn't strike me as particularly elegant, I'd appreciate suggestions for a nicer solution. This approach should if I'm not mistaken also work for native builds, so there's no need for the conditional, and maybe no need for to_c_array anymore.

The solution was suggested by Claude Opus 5.5 and reviewed and tested by me:

• For v0.22.0, the configure-time header holds the same bytes as the to_c_array output.
• On master I built the jsonnet CLI twice, once normally and once with -DCMAKE_SYSTEM_NAME=Linux (which sets CMAKE_CROSSCOMPILING while still producing a runnable binary). Both give the same output for an expression that uses the stdlib.
• conda-forge's linux-aarch64 cross build passes with the change applied as a patch (to be dropped when this merges or the cross-compilation issue is fixed in an alternate way).

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[gemini-code-assist]

Code Review

This pull request introduces conditional logic in stdlib/CMakeLists.txt to handle cross-compilation by packing std.jsonnet at configure time using CMake commands instead of running the to_c_array executable. The reviewer suggests a cleaner, unified approach: using a helper CMake script executed via cmake -P at build time. This works for both native and cross-compiling builds, avoids configure-time overhead, and allows for the complete removal of the to_c_array executable and its source file.

[gemini-code-assist]

Instead of having conditional logic for cross-compiling and maintaining the to_c_array C++ executable, we can perform the hex-packing at build time using a helper CMake script executed via cmake -P.

This approach is fully cross-platform, works identically for both native and cross-compiling builds, avoids configure-time overhead (since it runs at build time), and allows us to completely eliminate the to_c_array target and to_c_array.cpp source file.

# Generate a helper script at configure time to pack std.jsonnet at build time.
# This works identically for both native and cross-compiling builds,
# and avoids the need for the compiled `to_c_array` helper executable.
file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/pack_std_jsonnet.cmake" [=[
file(READ "${INPUT_FILE}" std_hex HEX)
string(REGEX REPLACE "([0-9a-f][0-9a-f])" "0x\\1," std_bytes "${std_hex}")
file(WRITE "${OUTPUT_FILE}" "${std_bytes}0")
]=])

add_custom_command(
	COMMENT "Packing std.jsonnet into std.jsonnet.h"
	COMMAND ${CMAKE_COMMAND}
		-D "INPUT_FILE=${CMAKE_CURRENT_SOURCE_DIR}/std.jsonnet"
		-D "OUTPUT_FILE=${CMAKE_CURRENT_BINARY_DIR}/std.jsonnet.h"
		-P "${CMAKE_CURRENT_BINARY_DIR}/pack_std_jsonnet.cmake"
	OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/std.jsonnet.h"
	MAIN_DEPENDENCY std.jsonnet
)

add_library(stdlib_h INTERFACE "${CMAKE_CURRENT_BINARY_DIR}/std.jsonnet.h")

[olantwin]

This alternative has been implemented in #1345