Rewrite generic compilers ("cc", "c++") to clang or gcc

depending on what these symlinks point to

3 files changed, 111 insertions, 0 deletions

diff --git a/src/compile.c b/src/compile.c
index f78faa2..96bed2c 100644
--- a/src/compile.c
+++ b/src/compile.c
@@ -25,6 +25,7 @@
 
 #include <config.h>
 
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -445,6 +446,86 @@ static int dcc_please_send_email_after_investigation(
     return dcc_note_discrepancy(discrepancy_filename);
 }
 
+/* Re-write "cc" to directly call gcc or clang
+ */
+static void dcc_rewrite_generic_compiler(char **argv)
+{
+#ifdef __APPLE__ /* FIXME */
+
+    assert(argv);
+
+    return;
+#else
+    char linkbuf[MAXPATHLEN + 1], *link = NULL, *t;
+    int ret, dir;
+    ssize_t ssz;
+    struct stat st;
+    bool cpp = false;
+
+    assert(argv);
+
+    if (strcmp(argv[0], "cc") == 0)
+        ;
+    else if (strcmp(argv[0], "c++") == 0)
+        cpp = true;
+    else
+        return;
+
+    ret = dcc_which(cpp ? "c++" : "cc", &link);
+    if (ret < 0)
+        return;
+    t = strrchr(link, '/');
+    if (!t)
+        return;
+    *t = '\0';
+    dir = open(link, O_RDONLY);
+    if (dir < 0)
+        return;
+    *t = '/';
+    ret = fstatat(dir, t + 1, &st, AT_SYMLINK_NOFOLLOW);
+    if (ret < 0)
+        return;
+    if ((st.st_mode & S_IFMT) != S_IFLNK)
+        /* TODO use cc -v */
+        return;
+    ssz = readlinkat(dir, t + 1, linkbuf, sizeof(linkbuf) - 1);
+    if (ssz < 0)
+        return;
+    linkbuf[ssz] = '\0';
+    fstatat(dir, linkbuf, &st, AT_SYMLINK_NOFOLLOW);
+    if ((st.st_mode & S_IFMT) == S_IFLNK) {
+        /* this is a Debian thing. Fedora just has /usr/bin/cc -> gcc */
+        if (strcmp(linkbuf, cpp ? "/etc/alternatives/c++" : "/etc/alternatives/cc") == 0) {
+            ssz = readlinkat(dir, linkbuf, linkbuf, sizeof(linkbuf) - 1);
+            linkbuf[ssz] = '\0';
+        }
+    }
+    ret = faccessat(dir, linkbuf, X_OK, 0);
+    if (ret < 0)
+        return;
+
+    if (        cpp && strcmp(strrchr(linkbuf, '/') ? strrchr(linkbuf, '/') + 1 : linkbuf, "clang++") == 0) {
+        free(argv[0]);
+        argv[0] = strdup("clang++");
+        rs_trace("Rewriting '%s' to '%s'", "c++", "clang++");
+    } else if (   cpp && strcmp(strrchr(linkbuf, '/') ? strrchr(linkbuf, '/') + 1 : linkbuf, "g++") == 0) {
+        free(argv[0]);
+        argv[0] = strdup("g++");
+        rs_trace("Rewriting '%s' to '%s'", "c++", "g++");
+    } else if (!cpp && strcmp(strrchr(linkbuf, '/') ? strrchr(linkbuf, '/') + 1 : linkbuf, "clang") == 0) {
+        free(argv[0]);
+        argv[0] = strdup("clang");
+        rs_trace("Rewriting '%s' to '%s'", "cc", "clang");
+    } else if (!cpp && strcmp(strrchr(linkbuf, '/') ? strrchr(linkbuf, '/') + 1 : linkbuf, "gcc") == 0) {
+        free(argv[0]);
+        argv[0] = strdup("gcc");
+        rs_trace("Rewriting '%s' to '%s'", "cc", "gcc");
+    } else
+        return;
+#endif
+}
+
+
 /* Clang is a native cross-compiler, but needs to be told to what target it is
  * building.
  * TODO: actually probe clang with clang --version, instead of trusting
@@ -608,6 +689,7 @@ dcc_build_somewhere(char *argv[],
     dcc_free_argv(argv);
     argv = new_argv;
     if (!getenv("DISTCC_NO_REWRITE_CROSS")) {
+        dcc_rewrite_generic_compiler(new_argv); /* does not work on Mac FIXME */
         dcc_add_clang_target(new_argv);
         dcc_gcc_rewrite_fqn(new_argv);
     }
diff --git a/src/util.c b/src/util.c
index 4b26fa7..c4939cd 100644
--- a/src/util.c
+++ b/src/util.c
@@ -574,6 +574,34 @@ int dcc_remove_if_exists(const char *fname)
     return 0;
 }
 
+int dcc_which(const char *command, char **out)
+{
+    char *loc = NULL, *path, *t;
+    int ret;
+
+    path = getenv("PATH");
+    if (!path)
+        return -ENOENT;
+    do {
+        /* emulate strchrnul() */
+        t = strchr(path, ':');
+        if (!t)
+            t = path + strlen(path);
+        loc = realloc(loc, t - path + 1 + strlen(command) + 1);
+        if (!loc)
+            return -ENOMEM;
+        strncpy(loc, path, t - path);
+        loc[t - path] = '\0';
+        strcat(loc, "/");
+        strcat(loc, command);
+        ret = access(loc, X_OK);
+        if (ret < 0)
+            continue;
+        *out = loc;
+        return 0;
+    } while ((path = strchr(path, ':') + 1));
+    return -ENOENT;
+}
 
 /* Returns the number of processes in state D, the max non-cc/c++ RSS in kb and
  * the max RSS program's name */
diff --git a/src/util.h b/src/util.h
index 463a383..92017c5 100644
--- a/src/util.h
+++ b/src/util.h
@@ -49,6 +49,7 @@ int dcc_get_dns_domain(const char **domain_name);
 void dcc_get_proc_stats(int *num_D, int *max_RSS, char **max_RSS_name);
 void dcc_get_disk_io_stats(int *n_reads, int *n_writes);
 
+int dcc_which(const char *cmd, char **out);
 
 int dcc_dup_part(const char **psrc, char **pdst, const char *sep);