RFC: Per-project sysimage

base/loading.jl

@@ -1495,6 +1495,50 @@ function stale_cachefile(modpath::String, cachefile::String)
     end
 end
 
+function _sysimage_path_slug()
+    ptr = @ccall jl_sysimage_path_slug()::Ptr{UInt8}
+    if ptr === C_NULL
+        error("`jl_sysimage_path_slug` failed")
+    end
+    slug = unsafe_string(ptr)
+    Libc.free(ptr)
+    return slug
+end
+
+"""
+    Base.project_sysimage_path(project::AbstractString = Base.active_project())
+
+A path to the file that stores the system image path for `project` that would be
+used by default.
+"""
+function project_sysimage_path(project::AbstractString = active_project())
+    if !isfile(project)
+        error("Non-existing project file: $project")
+    end
+    slug = _sysimage_path_slug()
+    return joinpath(dirname(project), ".julia", "sysimages", slug * ".path")
+end
+# This definition of path must be matched with `jl_resolve_sysimg_location`
+# in `../src/init.c`.
+
+"""
+    Base.set_sysimage_path([project::AbstractString,] sysimg::AbstractString)
+
+Use system image `sysimg` for project `project` by default, for this
+julia binary executable.  `project` defaults to currently active project.
+"""
+function set_sysimage_path end
+set_sysimage_path(sysimg::AbstractString) = set_sysimage_path(active_project(), sysimg)
+function set_sysimage_path(project::AbstractString, sysimg::AbstractString)
+    path = project_sysimage_path(project)
+    if !abspath(sysimg)
+        sysimg = relpath(sysimg, sysimg)
+    end
+    mkpath(dirname(path))
+    write(path, sysimg)
+    return
+end
+
 """
     @__FILE__ -> AbstractString
 

src/init.c

@@ -47,6 +47,8 @@ extern BOOL (WINAPI *hSymRefreshModuleList)(HANDLE);
 #include <unistd.h>
 #endif
 
+JL_DLLEXPORT uint32_t jl_crc32c(uint32_t, const char *, size_t);
+
 // list of modules being deserialized with __init__ methods
 jl_array_t *jl_module_init_order;
 
@@ -541,6 +543,38 @@ static const char *absformat(const char *in)
     return out;
 }
 
+static char slug_char(char i)
+{
+    if (i < 26) {
+        return 'A' + i;
+    } else if (i < 26 + 26) {
+        return 'a' + (i - 26);
+    } else {
+        return '0' + (i - (26 + 26));
+    }
+}
+
+JL_DLLEXPORT char *jl_slug32(uint32_t x, int p)
+{
+    const int n = 26 + 26 + 10; // length(['A':'Z'; 'a':'z'; '0':'9'])
+    char *out = (char*)malloc(p + 1);
+    if (out == NULL) {
+        return out;
+    }
+    for (int i = 0; i < p; ++i){
+        int d = x % n;
+        x = x / n;
+        out[i] = slug_char(d);
+    }
+    out[p] = 0;
+    return out;
+}
+
+JL_DLLEXPORT char *jl_sysimage_path_slug(void)
+{
+    return jl_slug32(jl_crc32c(0, jl_options.julia_bin, strlen(jl_options.julia_bin)), 5);
+}
+
 static void jl_resolve_sysimg_location(JL_IMAGE_SEARCH rel)
 {   // this function resolves the paths in jl_options to absolute file locations as needed
     // and it replaces the pointers to `julia_bindir`, `julia_bin`, `image_file`, and output file paths
@@ -570,6 +604,73 @@ static void jl_resolve_sysimg_location(JL_IMAGE_SEARCH rel)
         jl_options.julia_bindir = abspath(jl_options.julia_bindir, 0);
     free(free_path);
     free_path = NULL;
+    if (rel == JL_IMAGE_JULIA_HOME && jl_options.project && strcmp(jl_options.project, "@.")) {
+        uv_stat_t pathstat;
+        if (!jl_stat(jl_options.project, (char *)&pathstat)) {
+            char *project = strdup(jl_options.project), *projectdir = NULL;
+            if (!project) {
+                jl_errorf("fatal error: failed to allocate memory: %s",
+                          strerror(errno));
+            }
+            if ((pathstat.st_mode & 0xf000) == 0x8000) { // --project=$projectdir/Project.toml
+                projectdir = dirname(project);
+            } else if ((pathstat.st_mode & 0xf000) == 0x4000) { // --project=$projectdir
+                projectdir = project;
+            }
+            if (projectdir) {
+                char *slug = jl_sysimage_path_slug();
+                if (!slug) {
+                    jl_errorf("fatal error: failed to allocate memory: %s",
+                              strerror(errno));
+                }
+                free_path = (char*)malloc_s(PATH_MAX); // $projectdir/.julia/sysimage.path
+                int n = snprintf(free_path, PATH_MAX,
+                                 "%s" PATHSEPSTRING ".julia"
+                                 PATHSEPSTRING "sysimages"
+                                 PATHSEPSTRING "%s.path",
+                                 projectdir, slug);
+                // This definition of path must be matched with
+                // `project_sysimage_path` in `../base/loading.jl`.
+                if (n >= PATH_MAX || n < 0) {
+                    jl_error("fatal error: jl_options.project path too long");
+                }
+                ios_t pathfile;
+                if (ios_file(&pathfile, free_path, 1, 0, 0, 0)) {
+                    char *data = (char*)malloc_s(PATH_MAX);
+                    int n = ios_readall(&pathfile, data, PATH_MAX);
+                    if (ios_close(&pathfile)) {
+                        jl_printf(JL_STDERR, "WARNING: failed to close file %s\n", free_path);
+                    }
+                    if (n >= PATH_MAX || n < 0) {
+                        jl_errorf("fatal error: cannot read path from %s", free_path);
+                    } else {
+                        // Use the path in `$projectdir/.julia/sysimage.path`
+                        if (isabspath(data)) {
+                            jl_options.image_file = data;
+                        } else {
+                            char *basepath = strdup(free_path);
+                            if (!basepath) {
+                                jl_errorf("fatal error: failed to allocate memory: %s",
+                                          strerror(errno));
+                            }
+                            basepath = dirname(basepath);
+                            int n = snprintf(free_path, PATH_MAX, "%s" PATHSEPSTRING "%s",
+                                             basepath, data);
+                            if (n >= PATH_MAX || n < 0) {
+                                jl_error("fatal error: jl_options.project path too long");
+                            }
+                            jl_options.image_file = abspath(free_path, 0);
+                            free(data);
+                        }
+                    }
+                }
+                free(project);
+                free(slug);
+                free(free_path);
+                free_path = NULL;
+            }
+        }
+    }
     if (jl_options.image_file) {
         if (rel == JL_IMAGE_JULIA_HOME && !isabspath(jl_options.image_file)) {
             // build time path, relative to JULIA_BINDIR

src/jloptions.c

@@ -83,7 +83,9 @@ static const char opts[]  =
     " --help-hidden             Uncommon options not shown by `-h`\n\n"
 
     // startup options
-    " --project[={<dir>|@.}]    Set <dir> as the home project/environment\n"
+    " --project[={<dir>|@.}]    Set <dir> as the home project/environment.\n"
+    "                           If a text file `<dir>/.julia/sysimage.path` exist, its content\n"
+    "                           is used as the default value of of --sysimage.\n"
     " -J, --sysimage <file>     Start up with the given system image file\n"
     " -H, --home <dir>          Set location of `julia` executable\n"
     " --startup-file={yes|no}   Load `~/.julia/config/startup.jl`\n"